The CGI in RoTF looked just as good as TF1 to me.
Both movies had some spotty parts. Rotf moreso I guess because of the time squeeze.
Brawl/Devastator in TF1, when he gets shot and dies. I'm at a lost to come up with anymore at the moment.
Just about any scene with the Twins.
When Ravage is running towards the military base.
The part when Demolisher wrecks.
But I think the CGI in these films trumps anything else I've seen. I have yet to see Avatar though.