I've only played Ace Combat 6 ...but I feel like you're inside and interacting with an anime movie. The plot is cliche but relatively epic. By the end of the game you feel a sense of belonging with your sides fictional nation.
Don't have a PS2 or a XBox 360 to play some of the later versions on? I was watching some videos from earlier releases of the game and what strikes me as being most different is Ace Combat 6 on the 360 has much larger battles. There are dozens of fighters, helicopters, ships, tanks, and vehicles all going around at once in multiple battles. The earlier games are much smaller scale.
The large scale battles also look incredible...again because the missile trails are so beautiful!