Okay, so, here's my first post after years of lurking.
My top 10, based on an occasionally unhealthy CRPG habit of about three decades:
1) Angband: You could argue this back to Rogue, but this is the roguelike I spent the most amount of time on (and dozens of its derivatives). It has the largest amount of actual game-play content than just about any commercial release, and it is absolutely free. Some really extraordinary variants out there too. Part of what really appealed to me was the challenge level of it. It takes quite awhile to master, and satisfies the inner loot whore in all of us.
2) Wizardry series: Yeah, I'm cheating by putting several games in one position. This really set the bar for me as a kid for the kinds of games I enjoyed the most. Loved the challenge of the first three, and loved the interactivity/puzzles in Bane the most (that's the 6th).
3) Bard's Tale I & II: Yeah, cheating again by doubling up games. Absolutely loved what these games did with the Ultima/Wizardry formula. So much good content, challenging combat, riddles, mapping--just plain fun. The third one I believe had an automap feature and really seemed to dumb down the series for me. Plus an exploitable experience bug in the beginning and my complete lack of willpower in abusing it ruined most of the game for me.
4) Might and Magic 1 & 2: Again, loved the challenge of these games, the vast amount of content sans empty space (unlike most modern games that just manage to make lots of emptiness in their open world settings). I remember getting all excited looking at the maps that came with these games, because every square was packed with something interesting. I enjoyed all the other M&M games as well, but never felt the same level of challenge as in these two. Incidentally, I didn't beat either of them--got close to the end but gave up for some reason or another. I seem to remember in M&M II hating that encounters scaled a bit with levels--every random fight seemed to have +256 of something and I just got tired. But damn, what a game up until that point.
5) Wasteland: First non-fantasy CPRG that blew me away. Great content, puzzles, encounters, skill system, just lots of fun. Incinerating my entire party in a nuclear meltdown was an interesting little memory as well.
6) Planetscape Torment: Great story, writing, encounters, variety, humor, etc. Nice to play a game not catering to your average middle schooler. Definitely a favorite.
7) Baldur's Gate 2: I enjoyed the first, but as a AD&D nerd for many years, this game really nailed the high-level experience. Challenging fights and everything. Sad to say I never played the Throne of Bhaal expansion.
8) Deathlord: One of the few CRPGs that actually kicked my ass. I got really far in it too, but it was just absolutely brutal. I even returned to it on an Apple emulator some years later, got farther, but some nasty map puzzle made me shelve it for eternity. Still, loved the Oriental-themed take on the Ultima formula. And it had really cool new spells (this back in the days where the manuals were actually worth reading).
9) Ultima II-IV: I think II was actually my real favorite. Just something cool about stealing a phase blaster from a merchant and rocking the world with it for awhile. Loved how Ultima II mixed science and fantasy. III was fun for the variety it built upon the Ultima II formula, while IV was just revolutionary for the way it made you actually care about your decision making process. While I played most of them after IV, I didn't like how they kind of got away from imaginative fantasy to more of a Arthurian themed, real-world simulation. I like my fantasy to be a bit more escapist than that.
10) Eye of the Beholder: Just an awesome application of the D&D rules to a 1st person perspective. Plus the inclusion of an in-game contest on its release didn't hurt crazy players like me that prided themselves on finishing games in single, marathon play sessions. Yeah, that notion ended in high school, in case you're wondering. But 48 hours of nothing but quality CRPG goodness was as good as it got back in those days.
Honorable mentions:
Dungeon Master: I played this after EoB, not sure which was first offhand, but I loved what it did with the Wizardry formula, its skill building/spell casting system, challenging maps, etc.
Etrian's Odyssey I-III: Okay, I know, not a computer RPG but I never did specify what the "C" meant in my post, did I? This game takes the challenge of old-school and makes it fresh again. I love its built in map-building tools as well, and it comes from the days of quality over quantity. Great recent find for me.
Dark Spire: Another console game I'm slipping in this list, but again, like Etrian's Odyssey, does old school right. A few lame puzzles here or there, but overall one of the best game experiences I've had in years.
Demon Souls: I love the atmosphere of the game. Not terribly fond of action games and especially platforming elements (this had a few). Didn't finish it either--got fairly close, but couldn't beat those two demons on the narrow bridge--apparently this game punishes you for repeated failure by making the thing that kicked your ass even harder the next time. Died so many times to those two that it's probably better to start the game over. Haven't bought the sequel yet because I liked the first one too much to pass over it without winning.
Pool of Radiance: My favorite of the SSI Gold Box series. Just a great game, fairly lengthy, good character development progress, encounter variety, etc.
Phantasy 1-3: I just remember really enjoying these as a kid. Something cool about smashing a statue of Zeus, it coming to life, and getting to fight him. And even though the graphics were lousy, they do scaling right.
Phantasy Star 1-4: Somewhat challenging console games, fun character development.
Gothic 1 & 2: I know people are huge fans of these games on this site. I enjoyed the first couple quite a bit. Didn't feel different enough after those--I really like a sense of newness in my games--undiscovered creatures, areas, items, etc.
Anachronox: Great puzzles (Bepidris!), humor, combat. A consolesque game on a PC. Wish this would have had a sequel.
Fun trip down memory lane. Thanks for indulging.
-- Adam