NWN 2 is a very good game, especially with both the expansions. The first expansion, in particular, is one of the best I've played but is pretty dark. The second one is a great romp in the style of a good, old fashioned D&D table top game: less plot, more running around and you get to build your entire party from scratch if you want.*
Likewise, the first NWN is also pretty good, and also has a pair of great expansions. The problem with both might be that there may be issues with running them on W7. Certainly there were issues with the second game, particularly with the editor.*
The Baldur's gate games are great, but showing their age a little bit now. There's a new, ,upgraded version of BG1 coming out sometime soon on both the PC and the IPad so it might be worth checking that one out. It won't be much, but then, neither will a legacy version. The advantage of the new one is I assume it will have been retooled to work with modern resolutions.*
As for Planescape. Well, being a massive fanboi of the p&p setting I have difficulty looking past it. I think it's the best cprg of all time but I understand why you think it might be too much.*
You know what, any of these games are going to be hours and hours of fun. I don't think you can lose - as long as you can get them to run. Maybe check out Good Old Games.com, I think they sometimes work a bit of magic to get older titles running without too many issues on modern machines.*
Of course, you could always go buy him a copy of the Pathfinder rule book and some dice.....
