Of the games on your list, I'd go with either one of the Fallouts or Mass Effect 2.
The Fallout games are more RPGy but they have the downside of really needing to be modded; if you don't, you're missing out on half the game's potential. Mass Effect 2 has the downsides of being in the middle of a series, and the fact that its not particularly RPGy. But it is pretty easy to get into. The squad mechanics aren't terribly complicated, and if he plays on a low difficulty setting he can pretty much ignore them entirely.
If your friend is a Star Wars fan, I'd back up the thread recommendation for Knights of the Old Republic. They're both great games, though 2 is rather buggy and unfinished (I still like it better), so you'd need to acquire The Sith Lords Restored Content Mod.
As for the other games on that list:
Dragon Age: Origins is great, but I don't think its the best choice for a newcomer to the genre.
I second what GoodSamaritan said about BG, and what Maniacal said about the original Deus Ex. I've never played Invisible War.
Human Revolution is a good alternative to Mass Effect, and it doesn't have the same problem of being the second of a series.
If your friend prefers regular fantasy to retro-sci-fi, Morrowind and Oblivion are good. They're more RPGy than Fallout though. They suffer the same problem in that modding is really recommended.
I haven't played the others. I do own ShoC and The Witcher, but they're in my backlog.