If by "worth it" is it in the sweet spot for price and perfomance, no.
For a gaming system, around a $1,000 parts system you build yourself is the best value. You can get a good CPU and Video Card without going crazy to try to get the most frames you possibly can. For $1,000 you can even get a good size solid state hard drive along with 8 or 16 gig of RAM.
I would say 80% of the possible performance you could want is in that $1,000, then going up from there you are paying more for less and less gains.
Can a $2,000 system run a game smoother at top settings than a $1,000, of course. Will you be able to tell $1,000 of a difference between them if you have to drop the settings to High from Ultra? Probably not.