Depends on the game. Overall the i5's should be sufficient to deliver 60FPS in just about all new games, so the extra GPU power will help. However, CPUs tend to last far longer than GPUs, and the i7 could well last you 6-7 years, whereas you'll probably replace your GPU 2-3x in that period.
Speaking of which, we're about to get a new wave of GPUs, with the first die shrink in 5 years. This means a huge improvement in performance, and current cards will probably depreciate in value a lot. I would not recommend buying a high-end card right now, unless you're really desperate. Wait until summer when AMD and NV start releasing their new cards.