Well, I'm doing this in the reversed order. Rpg is by far my favourite type of games so it was pretty hard to narrow it down to 10 and I can't leave it without a honorble mention which goes to:
Baldur's Gate 1 which is a great game played in EasyTutu conversion with BG1 NPC mod,
Chaos Strikes Back which is one of the finest examples of oldschool hardcore rpg,
Albion which had pretty original setting with interesting and long storyline,
Ultima Underworld 1-2 which was not only technicially very impressive for the time of its release, but it also had good story, interesting puzzles and lots of atmosphere,
and Might & Magic 3 with all of its cool puzzle/riddle ridden dungeons.
Here's my top 10:
10. Arx Fatalis - this is a quite flawed game in some aspects but it has such great atmosphere that I can easily forget about them, I love those crypts!
9. System Shock 2 - great setting, interesting way of storytelling, well maintained atmosphere, interesting character development, this game is scary, along with Deus Ex my favourite sci-fi rpg
8. Deus Ex - well told and engaging story, interesting character development with some quite painful choices to be made by player, really a lot of possibilities how to solve problems, this is the game which was the most succesful at making me feel like I'm really there
7. Gothic - rather small but very detailed world, great story, cool characters, some nice puzzles, atmospheric dungeons, engaging combat, nuff said
6. Ultima 7 - this is a huuuge game, Black Gate is great for free-roaming, Serpent's Isle has more interesting world and is better focused storywise, though sometimes it's quite unclear what to do next. Showing the wooden sword to a dog was a bit too much for me, without a hint I would be probably stuck there forever. Lot of good dialogues, twists in the story and possibilities to interact with world easily make up for a bit weaker character development and messy inventory.
5. Wizardry 8 - I was playing the game without a walkthrough and it was quite frustrating experience because of all that combat standing in the way of continuing the story/solving puzzles, especially when I wasn't sure what to do/where to go next. Subsequent runs were much more fun for me because I could concentrate more on character development which is the game's main strength. There are some interesting mods for it, with Dodd's mod being by far my favourite.
4. Gothic 2 with NotR expansion - the expansion make the second Gothic a really great game. Lots of cool characters, challenging combat, superb terrain topology with some really atmospheric places. Chapters 1-3 are top notch, chapter 4 is great fun with Biff along, chapter 5 and especially the last one are pretty unsatisfying
though and I always breeze through them.
3. Baldur's Gate 2 - with a lot of great mods out there, this game has immense replayability value. I wouldn't rank the vanilla version that high because its main story is a bit on the weaker side and some recruitable characters are a bit underdeveloped in comparison with some others. Still, it is really impressive game.
2. Wizardry 7 - this game was insane. Great character development, massive world with carefully designed dungeons, all kinds of puzzles - not only the usual buttons, levers, keys but also adventure game types as well, covering the whole difficulty scale, strategic combat. Really, this rpg had it all. Without a walkthrough, it took me almost a year to finish.
1. Planescape: Torment - the only computer game which really moved me. Very original setting, ton of interesting characters/encounters, absolutely superb recruitable characters, awesomely astonishing storyline, well words fail me when I'm trying to describe this gem. This is a great piece of art and absolute pinnacle in computer game storytelling. After I've finished the game for the first time, I just sat silently for the whole night and thought about it all. All other games seemed so mundane in comparison!