I liked persona 3 the best. Give it a good graphics update and make the confidants - the social links - easier to max, and a few new personas and the game would be gold. Also, the whole male/female thing was only for the PSP version, which sucked. And, Thanatos was a b***h to fight if you weren't over lvl 70.
As for persona 5, it was quite easy. Good story, a lot of personas. DLC got kinda spendy, and there weren't nearly as many confidants as in 3, but a good game. Controls for the Monabus could have been better too.
I don't know much about the other persona games to be able to say anything about them, though I have done a little looking into persona 4.