both of those are excellent games, if you're bored with those genres though you should try Rpg's or the like, Mass effect is a good one to start you off as its also a third person shooter. oblivion holds the candles in RPGs to me and will for a long time coming, the most recent release is Dragon age: Origins, which is pretty cheap compared to MW2 £25 on play for this week, which i just bought but not played yet. thats made by the same people as Baldurs Gate, which if you are as big a gamer as you say should know that Baldurs Gate is the bomb.
the biggest advantage for RPGs to me though is the game length, you get so much more for your money, E.G. i enjoyed MW2 but finished it in 6 hours. Oblivion has been out for 3 or 4 years now, I've racked up over 100hours play time on it and not even finished the main quest. Fallout 3 is the same though more linear and quicker to finish.
Hope that helps you out.