Lair and gt prolouge are examples of games that support 1080p. Not all will since many are ports from 360 and it is the playstation's first year.
The odd thing with the PS3, that isn't a huge deal, is it's hardware scaler doesn't quite work properly...
On the PS3, it seems to lack the ability to hardware scale properly, for example if a game is rendered at 720p, it can't scale this to 1080p if your TV supports it, it will only output at 720p over HDMI, this is why on the back of games they usually will say it doesn't support 1080p.. that doesn't make it a worse game then the 360 version, it just can't scale the rendered output to 1080p for your TV...
The nuance is, developers can 'support' 1080p, like GT5 (The demo at least), by rendering at a resolution slightly higher then 720p to help the scaler work properly, and it can then upscale to 1080p, and the game can be classed as supporting 1080p.. however, that doesn't always mean it's rendered at that..
GT5 isn't true 1080p, in the same way Halo 3 isn't true 720p either..
What a game 'supports' and what it's rendered at internally can be two very different things..