Best games ever? Here's my top picks (yes, several of these have been mentioned already):
1) Fallout/Fallout 2. Great weapons, armor, story, setting, etc. And hey - you could get married in F2, become a &$@# star, and pimp out your wife! How's that for real role-playing? Not only that, but you could go through the game as various character types with wildly different options for some missions. Play a stupid guy, and the conversations get HILARIOUS! I also really liked Fallout: Tactics, although many Fallout fans were pissed because it wasn't the Fallout 3 they were waiting for.
2) Planescape: Torment. It's a Dungeons and Dragons game, but it's D&D like most people never play it. By far the best story telling of the Black Isle D&D games. You play an immortal, and you actually have to die at times to advance the plot. How cool is that?
3) Baldur's Gate Series. Yeah, it's AD&D, so if you don't like that, this isn't likely to change your mind. If you DO like that system, though, this is probably the best CRPG implementation of D&D that has been done. (IMO, Neverwinter Nights did not come close to surpassing it.)
4) Chrono Trigger. Best RPG on the consoles, bar none. Still worth playing even today.
5) System Shock 2. (The orinal was great as well, but going back and trying to replay it ruined my memories. The story was still good, but the user interface is SO outdated!) One of the scariest games I've ever played, with some AWESOME sounds. There's a mod that's been done to enhance the character models...
http://perso.wanadoo.fr/etienne.aubert/sshock/sshock_rebirth.htm
Also, some enhanced textures...
http://shtup.home.att.net/downloads/shtup_alpha002.zip
6) Deus Ex (Ooooo - a sequel is coming soon!) was a well done RPG/FPS hybrid, with skills and such.
Honorable Mentions:
Note - most of these are games that were GREAT (in my opinion) when they came out, but they're old now, and some people may not be very forgiving of the ancient graphics and sound.
The early Ultima games were great for their time. I don't know if I could still go back and play them, but Ulima through Ultima VI were great games and stories. The Guardian really took the series downhill. Also, check out Worlds of Ultima: the Savage Empire and Worlds of Ultima 2: Martian Dreams. Very cool games with great stories, they used a modified Ultima VI engine. (Worlds of Ultima 2 was written by Warren Spektor of Deus Ex fame. At one point in time, he said he thought it was the best story he had ever done.)
Wizardry series. Again, I don't know if I could still go back and replay them, but Wizardry 8 was a great send-off of the series.
Might and Magic III through V. They went downhill after that.
For sci-fi RPG fans, Shadowrun (SNES and Sega Genesis - the two are very different from each other) is pretty cool. Neuromancer on the PC is still a cool RPG/adventure story, but the graphics are ancient. These are two of the very first (and very few to this date) cyberpunk themed games I've played. If you like the genre, give them a shot.
There was a PC game called Hard Nova in the early 90s that I liked a lot. Also, there was a game done by New World Computing before they became part of 3DO. It was called Planet's Edge.
Finally, last but not least, if you like Fallout and Fallout 2, be sure to check out the original Wasteland: A Post-Apocalypse Adventure. This was done by several of the people who would go on to create Fallout almost a decade later. VERY old graphics, but it's still got a pretty cool story. (MANY similarities to the Fallout games.)