I love re4 and hate Zelda, but I'm not a fan of the Zelda franchise as a whole.
-Zelda is much longer, and depending on how much you like re, has much better replay value.
re has four modes (and my completion times, I'm mediocre):
Normal (18 hours, ok I kind of suck)
Professional (9 hours, better)
Assignment Ada (just over an hour)
Seperate Ways (4 hours)
-Graphics on re4 look to be a bit better, but it's a Wii either way, so don't get too excited.
-Controls are easy to get used to for both games, but if you haven't played an re game before you're going to hate the fact that you can't shoot while moving or strafe.
Zelda: TP is a classic on any Nintendo console, so I would pick it up. Resident Evil 4 is also a great game, but doesn't have as much credit as TP. Besides, TP is a long, action/adventure game that got a 9.6 on GameSpot! That's great!
You should get Zelda TP, it's a really good game, I have played it 4 times over and over. You probably will not ever see this game in the Used section of EB, mostly likely because no one wants to part with it.