Overg seems to be for those who appreciate FLIGHT simulators, rather than galaga shoot-em-up arcade games.
Firstly, after reading several negative reviews, it appears that the general consensus is 'actual flight simulators are not as much fun as good-ole starfighter for the gamecube.' Yes, if you appreciate two-stick twirrling shoot-em-up games where one can tap the 'fire' key with reckless abandon, then this game is certainly not for you. Pick up Ace-Combat 5, or perhaps Galaga, if you would like to enjoy one of these games. Although this game may not appeal to the bulk of our population, one should review it objectively, with its primary goal of flight simulation in mind.
If your major complaint was:
"All I did was: take off, find my target, fire my missles, evade theirs, and return home"
then you clearly shouldn't be playing fighter simulation games.
Secondly, I thoroughly agree that this game had ridiculously cheesy and downright stupid voice acting. I found myself rolling my eyes at the ridiculous attempts at drama. It's obvious that the game designers did not take these seriously, and neither should we. In all seriousness, if a person's major complaint is 'this flight simulation would be great if it had better voice acting" - then that person should not be playing fighter games.
In short, take it for what it is. If you want a easy/catchy shoot-em-up game, do not play OverG, because it's not for you. If you want a great Role-playing tear-jerking story, pick up Final Fantasy VII, and stop underrating OverG: a high-end graphic Fighter Simulation.