Will a n plus router be good for gaming

If your looking to get better speeds from the internet it ain't going to happen.
It won't make the internet any faster.
Your Cable/DSL connections only "averages" 2 or 3 Mbps so having a 300 Mbps N router isn't going to help.
But if you are having problems with "connection" speeds TO or FROM the Router it should be better. N has a farther reach then G so in that way it would help. If you get one of the MIMO type routers (or go with just a 5.0 ghz band "N") then you can get away from most of the interference from other devices. But ALL the wireless adapters on the devices have to have the same specs, MIMO, 5ghz band, N, etc, in order to use those features.
It all depends on how far away you are from the Router and how much interference you have from other wireless devices like a Microwave oven, cordless phones, etc. If you get an N Router you will have to have an N "adapter" with the X-Box/PS3/Computer to work (or they must be capable of N already).
It's mainly for streaming movies, music, etc, from your computer, etc, to a BlueRay Player, HDTV, etc.