Assassin's Creed has incredibly architecture, tons of extremely detailed character models on screen at once, complex interactions with the environment, and amazing lighting all happening at once (the lighting in particular is mind-blowing). Galaxy has what? Some nice looking textures? The Wii couldn't even handle the lighting effects Assassin's Creed uses, anyone who says that Galaxy looks even remotely close to Assassin's Creed is just plain delusional. Do yourself a favor- play Assassin's Creed up until you get to Jerusalem, then climb a building and look out over the city and notice the detail, draw distance, and lighting. The Wii will never, ever be able to do graphics like that. The end.
I'm not talking gameplay of course- Assassin's Creed was ultimately not that great of a game, and by all accounts Galaxy is an amazing game. We're talking PURELY graphics here.