Got to put in my recommendation for NWN2. I've been playing it, its expansions and some of the HUGE library of player-created modules for it for going on 3 years now with no clear end in sight. Truly great game (though buggy and poorly optimized to this day). The first Witcher runs on the same engine (though it runs much better on it), I happened to love that one too.
This is, of course, in addition to many of the other recommendations others have made previously.
This is, of course, in addition to many of the other recommendations others have made previously.