FPS games require more detail and more gfx quality.
3RD person makes sense if its vital for you to see what arround you...fighting games, melee fight in general or any swordfight. also group interaction is easier like in WOW.

3rd person can blend in the environment a lot better to the player character then first person. you interact with models and have a bigger impact on them (climbing, pushing,...)

i am not a big fan of switching views. keep one view works better for the atmosphere i think.


cheers