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.
Ditto to the TNG crew looking and feeling tired in NEM. I chalk it up to NEM being the end of their era. With all the actors knowing this would be there last movie and being away from Trek for some many years after INS they just didn't care as much. I still rate NEM higher than 09 since 09 just copied the dame format as TWOK and NEM. But the fresh young cast of 09 does make it fun and enjoyable to watch. Personally I think NEM could've been better if the supporting cast Riker, Troi, Crusher, Geordi and Word were given more to do. Make NEM sort of a goodbye tour before the whole TNG crew splits up. Have Riker and Troi on the Titan following the ENT to Romulus, have Geordi find a tactical weakness in the scimtar, have Word lead a balls to the wall charge against the Remans on the scimitar instead of Old man Picard, give Crusher and Picard a happily ever after ending as the only two who remain on Enterprise.