Is my HD picture a little fuzzy because it's 720p on a 1080p TV?

I just bought a 40" Samsung LN40A550 (a 1080p set). When I play 720p games or trailers on my ps3 (like Battlefield:BC or the Force Unleashed trailer), the picture appears a little 'grainy'. Is this because it's 720p material that's being upscaled to 1080p? And if so, is there a way to force it to be just 720p so it will look better? I mean, it still looks great, but it'd be nice to see it in its original form (without upscale degradation). I was worried it might have been a problem with the TV (like maybe i accidentally bought a poor quality tv), but i don't get the problem when viewing the XMB on the ps3, just when watching 720p material.