Broadly, there are two types of games that are important enough to remember years (or decades) later: those that are ground-breaking, and those that are good. Ones that are only breakthroughs can stay remembered for their historical significance, even though new iterations improve upon their formulas and eventually surpass them. Games that are good for reasons beyond being a technical breakthrough are the ones more likely to describe as "timeless" or "classic." Ultima VI sounds like an example of the first: quite a breakthrough in terms of mechanics, interaction, and storytelling at the time, but surpassed by later innovations. Starcraft (the first) would probably be the iconic example of the second: everything about that game already existed (in fact, it was somewhat obsolete on launch for still being 2D), and there has been tons of innovation in RTSes since then, but it was simply executed so well that it was not only remembered but actively played for over a decade.

In practice, many games are both. For example, the original Half-Life was a breakthrough for FPS games in tightly integrating an engaging story into the experience. Integrating the story in such a way has become standard fare by modern FPS standards, but Half-Life remains playable and enjoyable today. The graphics are dated (and a little painful), but the gameplay is rock-solid, and the story is still significantly better than 95% of what's on the market, both in terms of what the story is and how it's told. Deus Ex also ages well. It's gameplay innovation of putting RPG elements in an FPS game is now quite standard in FPSes, but the plot makes the game fun to play. Its gameplay innovation isn't really obsolete yet because there isn't something significantly better, but it is exceedingly common, and yet Deus Ex remains a better game than most other games that use it. I strongly suspect Portal will fall into this category as well--portals are cool, but when I think of Portal I think of GLaDOS and the Weighted Companion Cube. As a game, it is held up by way more than just a technical gimmick.

Unrelated: My personal favorite timeless classic is X-COM: UFO Defense (known as UFO: Enemy Unknown on the other side of the pond), which is apparently available now on steam, 17 years after its release.

I know it is all a matter of opinion, but as someone who dabbles in game development (I am an admin of the Dark Mists MUD, after all), here is my perspective:

If you look across the spectrum of oldstyle games, there are a few aspects off the top of my head that were responsible for our fun: challenge by control limits, challenge by time limits, and challenge by perfection (restarts, saves, etc).

Joust is a perfect example of challenge by control limits. You may accelerate left and right, you can bounce left and right, you can flap your wings to ascend or not flap to descend. This game is still fun for me because I understand and accept those limitations; they are almost the whole point of Joust. In many ways, Joust AI is predictable, so it is essential that you master the control. In other words, Joust is a game of skill!

The challenge of time limits is pretty obvious: You have X seconds to complete the level. In Joust, you have X seconds before eggs turn to soldiers or before the pterodactyl comes out (and he is killable if you have the skill). Time limits create stress; you want to beat the time limits. Some people rise to the challenge of completing things in the shortest time. Often, it is skill that allows you to surmount the challenge of time.

The challenge of perfection is provided by limiting restarts and save points. Some oldstyle games had plenty of restarts and saves, but they kept internal counters of your retries. They would reward you with certain kinds of endings, based on your retries. In Joust, you have X number of lives before you are forced to start all the way over from level 1.

Tetris is another great example of an oldstyle game that incorporates all three of these challenges.

One thing the game industry realized was that they could sell games to more people if the games required less skill, less challenge. Most games now practically walk you through them. What you do for fun is different now. Maybe you play to be an interactive (but aided) participant in a storyline. Maybe you play to be the first to finish the same progression everyone else can finish (WoW). Maybe you play because you want to see the latest pretty lights (aka advances in graphics) or have the stronger system, both of which are less about gaming and more about presentation.

Is it really that classic games are terrible or less fun than today's games? or is it more that the kinds of fun you can have with them are different from the kinds of fun you can have with today's games? As an oldschool gamer myself, I can tell you that I have gotten bored with some of the past approaches, but that does not make them suck. It just means that what I want has changed.

It all depends on what you consider a "classic" game. I can't play NES games anymore. But I still have fun with SNES games. I keep my SNES around to play games that I consider classic: Super Mario World, Super Metroid, Castlevania 4, Yoshi's Island, Chrono Trigger and Final Fantasy 6.

Also, if you like talking and reading about classic games, you should visit: http://www.gamespite.net

I still find enjoyable the following:

Star Force (1984, Tehkan, Arcade game)

Black Tiger (Capcom, 1987, Arcade game (2x Z80), 7 megabit ROM set)

Ninja Kid II (UPL, 1987, Arcade game)

Legend of Hero Tonma (Irem, 1989, Arcade Game)

Parodius Da! - Shinwa kara Owarai e (Konami, 1990, Arcade game)

Super Mario World (Nintendo, 1990, SNES, 4 megabit ROM cartridge)

The Legend of the Mystical Ninja (Konami, 1991, SNES, 8 megabit ROM cartridge)

Super Metroid (Nintendo, 1994, SNES, 24 megabit ROM cartridge)

Super Mario 64 (Nintendo, 1996, N64, 64 megabit ROM cartridge)

Castlevania: Symphony of the Night (1997, Playstation, CD-ROM)

It is possible to play it in its original form, and also in the PC, using emulators.

My favorite game of all time was made in 1998... 12 years later I still play it maybe once a year. Anyone else a big fan of Grim Fandango? I wish they would resurrect this game, or at least do an update to it like they did with Monkey Island.

By this metric "Citizen Kane" is dull, Beethoven's symphonies sound tired, and Phidias statues are so déjà vu. BTW did you read the Odyssey? Ha, they don't even have rail guns, stupid Achaeans!

I still love playing PacMan, etc. Actually I can't stand modern games at all out of the "casual" ones, because they're just too demanding, and I have no time to spend for this. I don't need any special involvement to play PacMan, Activision Enduro, or Intellivision AD&D. They're fun, anyway.

Yes, many classic games are terrible by today's standards. Even those of us who are old enough to have played these games when they came out, and who thoroughly enjoyed them, now consider them unplayable (or close to it), simply because many games have come out since that are better in every possible way (graphics, sound, playability, UI, ...). All in all, it's just a matter of expectations, and how they change over time.

Which makes me wonder, will today's games be considered unplayable 20 years from now? You'll explain to your (grand)child how revolutionary the Wii was when it came out, and they will just look at you funny, and throw away the controller in disgust after five minutes of playing on it?

Donkey Kong (arcade version) is still the only game that, in my opinion serves as a true metric of core gaming skills (tenacity, patience, hand-eye, etc)

New games won't ever come close to that era in regards to sheer difficulty

M.U.L.E.

Seriously, one of EA's first game releases from the early/mid 80's and I still play it on an atari800 emu.

Hell, Star Raiders and even Archon/ArhonII are pretty incredible still from that era.

The original Crystal Quest of the mid to late 80's on monochrome Macs and the early color version on the Mac II were great (but not MultiFinder compatible). Very addictive and fast/smooth which was a feat on the 8 and 16 MHz machines of the era. (Not to be confused with later rewrite which just wasn't the same)

Just the other day I was wondering about getting an old version of the OS running under SheepShaver to try it. I'll probably dust off an old machine instead.

I can't believe nobody mentioned nethack!

It's the most well-designed game I have seen to date.

I think a lot of the classic games are classics because they're universal and appeal to human natures desire to solve puzzles and best challenges. Games like Tetris will never get old because they're simple, easy to pick up, but you can always outdo yourself. Most games now cost $50-$60, last 5-10 hrs, and then you're done (generalizing here). I think that's way worse than classic games that I'm still playing 15 years later.

All creative endeavors must be judged inside a historical context. The movie "Citizen Kane" is terrible in terms of production value when compared to today, but in the historical context it was an amazing work of art that set the framework for many other movies to follow.

Timeless classic games:

- Super Mario 3

- Super Mario World

- Mega Man X

- Baldur's Gate

Still 100% fun. Dunno how they manage it.

one thing to recognize is that modern games generally have a lot of high-cost content. this is stuff that teams of 100+ people have to work on for 2+ years to make. so in that sense it would be really surprising if modern games didn't appear substantially better to us than in the past, when teams were tiny by comparison

I'm not tired of 2D side scrollers. I was so happy with the New Super Mario Brothers Wii. A trend I've noticed is that games who want to be modern but also 2D, simply render sprites in 3D but keep the game play 2D. (kirby 64 crystal shards, super smash brothers). It's great to see 2D gameplay is not dead.

I tried to play Wolfenstein 3D the other day... No strafe. :(

It would still be a great game if it only had strafe.

I still have a lot of fun with Thrust, Repton and Blockout, all of which have crappy graphics.

The Infocom games are just as good as ever. And the graphics are still top-notch.

My friends on steam started to comment about how many times they see the popup that I'm playing X-COM: UFO defense, so I had to stop.

The original Crystal Quest of the mid to late 80's on monochrome Macs and the early color version on the Mac II were great (but not MultiFinder compatible). Very addictive and fast/smooth which was a feat on the 8 and 16 MHz machines of the era. (Not to be confused with later rewrite which just wasn't the same)

Just the other day I was wondering about getting an old version of the OS running under SheepShaver to try it. I'll probably dust off an old machine instead.