These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
YMMV: Ace Combat Assault Horizon
Broken Base: Gamers that bought Assault Horizon BEFORE picking up any of the other games will love it. Most Long time fans hate it.
Stopping an ICBM launch by slipping under the missile's wake and accelerating upward after it, getting close enough to take damage from the thing's exhaust.
Engaging in a dogfight within the outer edges of a Category 5 hurricane.
Rescuing Guts when his ejection system is damaged by using his cannon to shoot off the canopy on Guts' Raptor.
D-Ray gets one himself, when, during the Moscow assault, enemy long-range SA Ms take out several helicopters and force all other choppers to duck down to avoid being targeted. Realizing that the mobile SAM teams will obliterate the fighters when they get back from refueling, D-Ray and his gunner Jack hunt down and destroy all the mobile SAM teams. And then, just as a final kicker, devastate the remaining rebel forces, essentially winning the battle single-handedly.
Game Breaker: Those Quick Air-to-Air missiles that were dreaded online and were the most broken missiles in the series? Yeah, they've been buffed back to AC 4 status, and when in Dogfight Mode, the reticle stays glued to the enemy plane you're targeting.
Double goes for the CFA-44 Nosferatu from Ace Combat 6, though the All Directional Multi-Missiles have taken somewhat of a Nerf.
Mis-blamed: As stated in the trivia section, Jim DeFelice had plans for a story set in the Strangereal setting, but the decision to go into the real world was Project Aces'. Forum hopping on GameFAQs has people up in arms with regards to DeFelice's story for the game.
Of course, this fight can be cheesed if you either a) bring an aircraft that has ECM, or b) learn to exit Dogfight Mode whenever you hear the lock-on beep and enter it again to make the missiles useless. Or you can do both to be sure.
That One Level: The AC-130 Level is damn near impossible in Ace Difficulty, because there's no way to prevent being shot at with SAM's from the ground and the SAM's are too fast to be shot. Couple that with the fact that you have to deal with two or three at a time, that two kill you and that you have to escort your allies, it's pretty hard.
They Changed It, Now It Sucks: Where to start... many AC fans are unhappy about the change in setting, the lack of superweapons, the introduction of Close Range Assault, the Regenerating Health and the addition of piloting different kinds of aircraft like helicopters and bombers, for starters.
HAWX was deemed inferior to Ace Combat by AC fans, yet many old-time AC fans think that HAWX is superior to Assault Horizon. It's more of a "It's a completely different game with a completely different gameplay" than complaining about the changes, though.