In no particular order:

Geneforge 1 or 4 - I really liked the whole series, but loved 1&4 best
Final Fantasy Tactics - my favorite FF game, I've always got a save going
Pool of Radiance - tactical goodness
Morrowind - my favorite open world game
Paper Sorcerer - really good modern dungeon crawler

1 - Morrowind - My favourite game of all time. The freedom, the factions, the quests, the exploration, the moddability, the everything.
2 - Dragon Age Origins - I absolutely loved how the story was different depending on your background, loved the choices I could make, loved my companions, loved everything. Heck, I even loved DA2. It was inferior, yes, but still, it was a good game on it's own. I also LOVED Inquisition, say whatever you want :P
3 - Divinity Original Sin Enhanced Edition
4 - The Witcher 3
5 - Baldur's Gate 2

Honorable mention to Loren the Amazon Princess, which is a Visual Novel-RPG, but I just had to mention it, because I've finished it so many times that I'm ashamed to admit......

1. Persona 4 Golden - all the goodness of Persona 4 with... well, with more Persona 4. Quite aside from being *the* best RPG for me, it's also the best example I've seen of 're-doing' a classic game.
2. Xenoblade Chronicles - For 2 weeks, this consumed my life. I laughed, I cried, I cheered, I sat there staring at the screen until someone came along and kindly picked my jaw up off the floor for me. This alone was a reason to own a Wii.
3. Persona 3 Portable - No, the Persona games are not the same thing rehashed each time. They are all different games with similiar mechanics. The Portable edition wins out over the FES edition for making combat better, including an entire new story path for a female protagonist, and for having extra songs. And for being portable!
4. Dragon Age Origins - I've lost count of the number of times I've played this. This game would win if it was purely about number of hours sunk into a game. It doesn't get old.
5. Mass Effect 2 - As much as I love all the Mass Effect games, this one wins out for it's structure, pacing, and especially it's characters.

Honourable mentions go to Planescape:Torment, Final Fantasy IX, Baldur's Gate II : Shadows of Amn, Witcher 3, and Guild Wars 1+2 (there's more than enough single-player story content in those games to qualify, even if they're MMO-style games)

I don't know who I would put on top, so it's better if I do this: in no particular order:

Planescape Torment
Arcanum: Of Steamworks and Magick Obscura
The Witcher Series
Deus Ex
Knights of The Old Republic( both games) and Chrono Trigger

In random order:
-Deus Ex
-Fallout New Vegas
-Dark Souls
-The Elder Scrolls: Morrowind
-System Shock 2

Too many to count. So I will go with the first thing in my mind.

Morrowind
Dragon Age Origins
Fallout 1
World of Warcraft
Papar Mario Trilogy

Sorry but a top5 is too small for me. Waaaay too small. Even with a previous top10 thread, I struggled when I chose games. Make it a top20 and we'll talk. :P

In no order, Chrono Trigger, FF6, Valkyrie Profile, Fallout, Ur-Quan Masters.

My list of RPG :

- Divinity Original Sin
- Oblivion
- Mass Effect 1/2/3
- Dark Messiah of Might and Magic (sort of RPG)
- Summoner

1. Ultima 7
2. Vampire Bloodlines (with all community patches)
3. System Shock 2
4. Fallout 2
5. Ultima 5 - Lazarus (though that is a mod)

And if mods don't count I would have to decide between Gothic 2, Baldur's Gate and Planescape Torment for that spot.

In no specific order, except Fallout 2

Fallout 2
Arcanum
The Witcher series
Morrowind
Divinity OS

1. Baldur's Gate
I think it's the right mix of exploration and having a strong storyline. The graphics are beautiful. The music is beautiful. It is very immersive. But that pathfinding though... Baldur's Gate II fixed the pathfinding somewhat, but lost the great music (different composer) and it is quite a bit more linear.

2. Might & Magic VI: The Mandate of Heaven
Great mix of dungeon crawling, open world exploration, and atmosphere. It is a very detailed and immersive game. The music is incredible. Best game music ever. There isn't much a main storyline though.

3. Xenoblade Chronicles
Incredible setting. Beautiful and unforgettable scenes. I was only bothered by the rigidity of the story presentation; it doesn't fit with the open world and exploration.

4. Phantasy Star Online: Episode I & II (Gamecube)
Best Diablo-like game ever. The local multiplayer (splitscreen) is pretty bare bones though and has camera issues.

5. Arcanum: Of Steamworks and Magicka Obscura
Combat is worse than Fallout, but overall Arcanum is a better game.

Honourable mention: Baldur's Gate II: Shadows of Amn, Diablo II, Fallout, Icewind Dale, Jagged Alliance 2, Paper Mario: The Thousand Year Door, Wizardry 8

I still haven't played many 80s and 90s RPGs. No Might & Magic 4+5, Ultima VII + VII-2, Ultima Underworld or Wizardry 6 or 7.

I also yet to play Fallout 2 and Planescape: Torment even though I owned them for years.

1. Arcanum
2. ToEE
3. Avernum
4. Gothic
5. Fallout

Mentions: MM series, Divinity, Daggerfall, Ultima IV-VI, Ultima Underworld 1-2, Kotor, Two Worlds, Lords of Xulima

The top 3 for me are easy choices.

1) System Shock 2. Umatched atmosphere and immersion. I've never been so drawn-in with any other game, that I really felt like I was in the gameworld while playing. Far and away my favorite overall game, RPG or other, of all time.

2) KOTOR. Greatest strory/characters/gameworld/dialogue combination I've seen in a game. 2nd favorite overall game of all time, definitely more of a straight-up RPG than SS2.

3) Baldur's Gate series. Most compelling combat I've experienced in a computer game. Everything else is absolutely top-notch as well across the board. Easily #3 all-time.

Picking the next best 2 gets a little more debatable, but I'll go with:

4) Vampire the Masquerade: Bloodlines. Awesome gameworld in a realistic modern city and overall unforgettable experience. And I'm not even a vampire movie guy.

5) Morrowind. Incredibly unique, massive and alien-feeling gameworld. Needs mods to really shine though, which is why I have to put it as a debatable 5th. My favorite open-world experience, despite kludgy/simplistic combat.

Honorable mentions to: The Witcher 1 (haven't played TW3 yet) for overall experience. Icewind Dale for it's combat, super-compelling encounter areas and the ability to create 6 unique characters yourself. Fallout 1/2 for immersive atmosphere, gameworld and story. Any of these could substitiute for 4-5.