I might as well post here, since I haven't played enough RPGs to come up with top 10 (let alone, top 5).
1. BG2 SoA + ToB with/without mods - I doubt any game will be better than this one in my life time. I have to admitt I'm biased towards this game though — this was my first ever RPG experience and I'm glad it was BG2. This game is reason I still play games.
2 & 3. Dragon Age: Origins + Awakening & Mass Effect 2 - This is really embarassing — I was a big Bioware fan girl. Funny, now I'm starting to hate where Bioware is heading. I couldn't really decide which game is better of two because of following reason. I LOVED ME2. I was so hooked up, I even quit WoW. I loved each mission (apart from PROBE LAUNCH), every companions and especially I LOVED MY FEM SHEP. But I just couldn't replay it. Period. I didn't see any replayable value in this game. On the other hand, I didn't love DA:O+A as much as ME2, but I liked the lore (how it is similar to D&D setting but not), liked companions and most of all, the replayability (especially compared to ME2). Mind you, I'm a big sucker for fantasy setting rpg with fun joinable NPCs.
4. NWN1 - I'm only putting this game up here because of mods. I absolutely loved some of mods I've played (especially, Shadow from Soul on fire and A Halo of Flies - both by Chris Huntoon). I haven't finished OC because I hated it and I finished SoU and hated it. I heard HotU is quite good but I got overwhelmed at first chapter and by the time I got to second chapter I was already getting sick of the game so I didn't finish it.
After this, I can't really think of games I really enjoyed. There are few games which could have made it into top 5/10 but didn't for several reasons:
PS:T - I loved story, but didn't enjoy the game. The sheer amount of texts was overwhelming and I got fed up with reading texts after texts on PC screen and a lot of times I got frustrated when dialogue started to go in loops. My poor English (especially back then) didn't help either. I did manage to finish this game, but skipping a lot of texts and heavily relying on walkthrough. I enjoyed and appreciated PS:T a lot more when I downloaded the pdf version and had a read through it like a book. Another minor reason that I didn't really enjoy this game was that, this game felt like it's for men, not women. I didn't feel comfortable playing role of a male protagonist and I didn't really understand charm of certain companions — especially Annah and Fall-From-Grace.
NWN2: MotB - I liked story of this game, like PS:T. I didn't enjoy this game for different reasons to PS:T though. I hated game mechanics. D&D 3.5 edition was too fiddely and hard to understand for me (I don't really like hardcore combats) but most of all, I hated the clunky interface/engine itself. It was extremely laggy and it wasn't like graphics were fantastic. Ultimately though, I gave up on this game because of the spirit eater mechanic. I got most of surviving tools by the time I quit (satiate and whatever else they were called). But I got stuck in a situation where if I don't rest, I will die from next battle due to low hp and ran out of spells. At the same time, if I rest, I would die anyway from hunger.
Other games I quite liked but wasn't as impressive to make it to top5/10: BG1 + TotSC, Diablo1, IWD series, ME1,
Games I disliked: DA2, The Witcher, Jade Empire, NWN2 OC, Drakensang 2
Games I really want to try in future: TES series (especially Skyrim & Morrowind), Fallout 3, and Arcanum.
I'm embarassed to say, I haven't had a proper go at any of TES series. I played both Oblivion and Morrowind, but all I did was download pretty hair/dress mods and barbie fun housing. Once I get new PC, I want to have a proper go at Skyrim. If I like Skyrim, I would like to have a go at Morrowind as well as I heard it's more hardcore than later 2.
Also, never tried Fallout series! Fallout game is in just about everyone's top 10 and I've never played a single on of them. My hubby as both Fallout3 and NV but he's recommending me to play FO3. So I will try that one as soon as I get new PC as well.
In addition, I've never had a proper go at Troika games either and at least 1 of 3 are in most of people's top 10 favourite. I decided to go for Arcanum because I'm not too farmilar with Vampire setting and I heard ToEE is for hardcore combat players (which I am not).
Divine Divinity was another that wanted to try but decided not to because it seems hardcore combat RPG as well.
I would have played KotoR1 but it broke my PC…. 'tis the reason I'm stuck with laptop at the moment, so no go with KotoR. I installed bloody game and it crashed 5 sec into the character creation (mind you, I did patch it to latest). So I reboot PC and try it for second time and I get blue screen of death about 2 minute into character creation. Next thing I know, I started to see artefacts even while booting Windows. Thought maybe my video card died so replaced it with new one and still same problem. Then I tried lots of troubleshooting ending up unclicking write combininb and it seemed to fix problem for few days. Then my PC just completely died. Won't even boot. So yeah. I hate KotoR >.>