...Or that's what IGN called it anyway. Here's my two cents:
First, the graphics and level design, since it's complained about very often. Even by PS2 standards, the graphics aren't great, and many levels are not so much repetitive as they are dull and uninteresting visually. However, this does not detract from the extremely fun and effective combat system; mostly because you're focused on beating up a variety of quirky thugs and not the landscape. The visuals aren't great, but they don't spoil the game if you just look past them, which is pretty easy with the fast-paced action God Hand offers.
Following onto my second point, the combat system is probably God Hand's greatest merit. Gene's moves are entirely customisable which gives you a huge amount of freedom on how to take down enemies and bosses. There is always a wide variety of moves to choose from at the store, but Gene also comes with several "free" moves that are useful throughout the entire game. This gives a total of 11
actions to choose from (punch, kick etc.) at any one time. The system also largely works defensively, giving you three different dodges you must use effectively in order to survive. Roulette moves, though rare, decimate your enemies in a very
cool fashion; ditto for the God Hand itself. Combined, combat becomes varied, thrilling and enjoyably challenging.
Other major aspects of gameplay don't shine as much, but still aren't bad overall. If you die, you won't get as large a bonus at the end of the stage, BUT you keep all the money you've collected thus far which often outweighs the bonus. However, this is often irrelevant since you can keep save-reloading your trips to the casino, giving you virtually unlimited money. Movement might be a pain at first, but after some getting used to it becomes entirely possible to manage. The Fighting Ring is also a great addition for trying out new moves, earning money and challenging yourself.
Lastly, the difficulty. The level system helps you quite a bit since you lose levels faster than you gain them, meaning that the game will always lean more towards "easy" than "hard". The enemies may seem a bit cheap, especially in groups, but the game is quite beatable at low levels. Learn the controls (especially dodges) and you'll do fine.
Overall, an enjoyable, challenging yet rewarding game.