depednign on the resolution for games. the GT 650m can generally get games on 1336x768 on high settings on the heavy games. If you dont mind having the settings maxed in gaming, then it can fit your need.
-As far as the game you listed it seems fine.
-For HD video editting, you might have some small issues with the 650, its not a workhorse GPU.
-Watching HD movies, you would be-able to watch 1080p, it would just scale down to your resolution of 1600x900.
-Multitasking shouldn't be a problem.
Other than the 1600x900 resolution, the laptop seems fine for your needs.