They completely botched up the GBA Gunstar Super Heros review, because they were judging it more on their memory of the first game, and not this game as a whole.
They actually gave points away because it didn't surpass their memory of the original.
I'm sorry, you judge games on their own merit only, not if they compete with a memory of the prior game.
If they did that it's indeed bad. I've played both at the same time (well, GFH first, got GH a day or two later) and IMO Gunstar Future Heroes easily surpasses its predecessor (except for the awful, awful Moon 2 Stage 1). Sure, it has no two-player mode but how many would use multiplayer on a GBA game like that?
Sure the graphics are barely better. So are the X360's and the PS3's. You need a few orders of magnitude more power to archieve a jump that qualifies as more than "barely".