I think the TNG cast are all superb in First Contact and Insurrection. Only criticism to be made is that Marina Sirtis is playing herself and not Troi but I'm not much of a Troi fan so I can't say I mind.
The character of Picard is supposed
to be acting out of character in First Contact so I let it slide. We're supposed to be finding his attitude wrong when he goes all "I WILL MAKE THEM PAY FOR THAT THEY'VE DONE!". His obsession for revenge isn't supposed to be some gung-ho thing we cheer at like people on this forum make out, but something that shocks us so we're pleased when he comes to his senses at the end.
In Nemesis everybody seems tired for whatever reason. I still rate the script above Trek 09 and Generations which are the weakest movie scripts, but the production itself lacks the energy of the previous 2 movies. It's not an awful movie but every time I finish watching it I just feel tired. Every time I finish Generations I feel pissed off and fed up though so at least it's an improvement on that.