I enjoyed both games from what I've played. I beat HL2 but never beat Far Cry (only because my computer crashed at the time and I haven't reinstalled it yet).
With that said, there's a little known FPS that came out in 2004 that I enjoyed more than Far Cry and HL2. Chronicles of Riddick : Escape From Butcher Bay was more entertaining than both of those games in my opinion. I never got bored with any parts in COR:EFBB. There were some parts in HL2 that I just found tedious...the boat ride and the end of the game. It seems that Far Cry is the same way from several posts.