Hum. I liked DA:O but not the combat mechanics;
What didn't you like about them? I thought it was the best RTwP system I'd seen since the IE games, even though it was certainly rough around the edges (the movment limits on a zoomed out camera were certainly annnoying).
Character customization also could have use some serious improvements. I also wasn't a big fan of brinding the "holy trinity" from MMO games into it (tank, healer, dps...) with related skills.
I thought ME1-2-3 were fun (I think i enjoyed ME-1 the most but I had no regrets with ME-2,3). The problem with NWN1 vs NWN2 is polar opposite. The community loved NWN1 because the tools were very good but teh 'demo' campaign really sucked; NWN2 had a better campaign but the tools really sucked

Indeed, most that consider NWN "good" are having memories of what was possible with the toolset. The campaign itself was crap.
After ME1 the story seemed to go all over the place, later I learned that the guy who wrote the story for ME1 left BioWare after ME1, this explains a lot (the "main" story for ME2 was rather weak but I enjoyed the combat mechanics; ME3 was just weak all over compared to ME1 & 2, story and mechanics respectively).
Anyway, I've written a lot about what was wrong with ME2 back in the day on BioWare's forums and they managed to do worse on pretty much every count in ME3 (weaker combat, shallower characters, ignoring choices you made in previous games, ignoring events from previous games, removing even more character customization,...)
I'm trying to decide on the last RPG I really liked; the thing isthat I played DKS late (after DA:O) and enjoyed it significantly more; I played ME-3 just about 6 months ago and liked it but not as much as DKS; and I'm not sure we can call games like king bounty and space ranger 2 RPG but if so I really like king bounty series ('cept the last one which sucked worse than bad)
DA:O had a lot of potential but they made the same mistake as with NWN1 (though at least the storyline was better and you did have a party) in that you have a bunch of locations you are forced to visit and have pretty much no sidequests at all. I think BG2 nailed it in this repsect as your main quest is only a small part of the game and you are free to explore the huge amounts of big sidequests there are without descending to Elder Scrolls level of generic quests/characters (name 3 characters in Skyrim you care about even in the slightest, I could give you a whole lot more than that from BG2)
The thing is that I can't think of any recent games by Obsidian that I've played. Well I did play dungeon siege which was ok and I liked nwn2; but i missed fallout las vegas; and I think that is the game most people think as obsidian last major effort (well south park but that isn't out yet).
Fallout: New Vegas was way better than Fallout 3 story-wise (and way better than Oblivion/Skyrim, but that's not hard), but suffers from having to use Bethesda's tech, with all the usual bugs (and then some, Obsidian and Bethesda are both known for their uncanny ability to create buggy games).
If you played all of Oblivion, Fallout 3 and Skyrim then F:NV just feels too similar. Personally I got burned out on it (I'm very far in and have completed most DLC, but still have to finish up the main campaign...and I started playing it on release, insofar possible with all the bugs it had then).
Dungeon Siege 3 (at least I think it was 3) is just a generic hack and slash, didn't (and still doesn't) interest me at all.