The only game I'd give a perfect 10 is Pokemon red/blue.

It was flawless. The only glitch was the missingno glitch but it was fun to use!
Not only was it really good but its still really good. Seriously i just finished playing blue for an hour. It is still fun. I've had it since i was about 8 and i play it now when I'm 16. Its challenging, rewarding, entertaining.

The closest games to a 10 I'd give now are:

CoD4 - 9.5
Uncharted - 9
Resistance - 9
Oblivion - 8.5
Halo 3 - 8.5

I'm back...