Ultimately, what I've seen from people who have played both is that people tend to prefer P3's ending to P4's. It's something close like 60%, anyways. I think it's the same for those I've seen who've played P2 and P4, but I don't know about P1.
I'm going to make a random poll I made on another forum once, and the results of this will determine whether I freak out or not (or confirm certain suspicions):
http://www.poll-maker.com/poll403010xf7eb4641-15
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Ooh boy
P3's awakening is obviously the GOAT. It's held back by its poor animation quality, but as far as atmosphere, direction, and music go, it pretty much nails everything. The build up before he actually pulls the trigger is especially great. The heartbeat, the wavering in his eyes, the sweating, the hesitation, the overall tension...
it's all so good. The movie version does a few things better (Animation quality and Makoto's expression after he pulls the trigger) but it's longer and more drawn out, and it misses few of the things that made original special.
P4's awakening is pretty damn great. It's more succinct and tighter than P3s. The animation is obviously better and the musical progression is pretty much flawless. I especially like Yu's jubilant demeanor after he flips the card over, and this shot is godlike. Nowhere near as tense as P3's, but it's still pretty good.
Even though I prefer 3, both of them are really great. There's this inhuman quality that Yu and Makoto after immediately summoning their Persona that immediately sticks out for me.
The Answer's awakening is alright. It has tension and the animation is pretty good, but there's just way, way too much talking (and the dialogue is kind of cheesy) The lack of music is bummer and I don't find Metis to be all that threatening. Aigis's summoning of Orpheus itself is also pretty boring. It lacks the quirks that made Yu and Makoto's awakening stand out.