Back when I played it on the PS2, I felt the bosses were the game's one weakness. The 1-player game would roll along just fine and then come to a dead hault after reaching the boss.
I'd agree with this.
For me, I just hate the fact that the feel of the game and the flow of its play changes completely when you reach the boss.
Most of SNK's bosses feel like that to me. They feel like 'dumb' hard challenges, as though the designers felt they couldn't deliver an exciting climactic battle without completely throwing out all the gameplay that was so fun leading up to the fight and replacing it with a nonsensically hard challenge.
Mind you, I am still a SNK fan and I like the majority of their bosses on a conceptual/aesthetic level, but the challenge curve is just not commensurate with the game's experience overal, IMO.
EDIT: Survival Achievement GET!
The trick was to just open up big on the bosses. Not hard at all. Got 27 rounds on Survival completed, going through all bosses in the course of that, without much difficulty.
While the endings REALLY, REALLY suck in this game, I think it's bollocks you can't view them in a gallery. Good thing the internet exists for this sort of thing.