So what are the best Ace Combat games to play? I have a PS2 and PS3.
5 > 0 > 4.
If you play only one, play 5.
Here is my somewhat spoiler-free review.
I would agree that 5 is the "best" game, all-around - and I say that as someone who enjoys Zero more. 5's gameplay engine is much improved over 4's, and there's a much greater complexity of missions in 5 than there is in Zero or 4. It's the biggest and meatiest of the three. Ace Combat always has had great music, but 5 introduced the
Unsung War motif which is used in Ace Combat Zero and appears briefly in the trailer. It shows up a bit in Assault Horizon, too.
The one thing I disliked was 5's story. It was just too melodramatic for me at times, and the writing has a few cringe-worthy moments. I think this is a weakness that all the games share, but this was particularly noticeable in 5 given the scale of the game and the themes of the plot. They set high goals and didn't quite meet them. In terms of story-
telling, I preferred 4's comic-book style and Zero's documentary style over 5's. A silent/invisible protagonist makes sense if the story is being told after-the-fact (as it is in 4 and Zero), but when the player character is an active participant in the story as it is being told, it feels a little weird to never see him.
Zero focuses heavily on dogfighting, and in light of this certain stylistic decisions make a lot of sense: the story is told in a series of interviews by your defeated enemies. Unfortunately, it doesn't have the diversity of missions that 5 has, so in some respects it felt like an expansion pack (to 5) rather than a standalone game. Further, there are so many "ace" pilots introduced, none of the characters really stand out the way the Yellow squadron does in Ace Combat 4, with one exception (who IMHO is the most memorable character in the series). I remember reading somewhere that the original intent was to include worldwide multiplayer in Ace Combat Zero, which would've greatly elevated the game for me.
IMHO, the perfect Ace Combat game would have 5's scale/missions and gameplay, with 4's plot/superweapons, and Zero's lore/characters.
I've said nothing of 4, because I've already written too much.