RE4 is one of those games that fails at what it should be doing - i.e. scaring you - but still manages to be brilliant because it's just such massively stupidly fun.
You start the game fending off a horde of zombies (some wielding chainsaws) using one pistol, a knife, possibly a shotgun, and rapidly dwindling ammo. FUN.
The first boss is giant sea monster who tries to eat you, and who you defeat using harpoons and a tiny wooden boat like some third-world whaler. FUN.
Later, you fight zombies who look more like Wolverine from X-men and can stba you through the face if you get too close. FUN.
I could go on, but the point is that RE4 succeeds where the other games fails because it doesn't ponce around trying, and failing, to create atmosphere with what it acknowledges is a hilariously unfrightening plot. Instead, it just says "Here are some zombies, here are some mutant freaks, here is a gun. Now go save the president's daughter."
Get it if you can and get it on Wii, it's one of the games that actually manages to get the control scheme to work pretty weel without being ridiculous, graphics are decent for a Wii port of a Gamecube/PS2 game and, y'know, it's nice to have a decent Wii game that's not a first-party title.