RE4 is a must! It is a 20hr game on your first run through, and you will likely run through it another 2 or 3 times. imo it has the best replayability out of all the available wii games. And there is lots of incentive to play the game a 2nd and 3rd time (but I won't spoil it for you). Also, there are side missions once you've completed the main game, and also mini games (the mercenaries) which are really, really fun because you can play different characters.
RE4 is one of the best games of all time, and easily in the top 3 for wii games... it's just that good. you will get hours and hours of enjoyment out of it, and even when you've played it to death... you'll pick it up in another 3 months to play through it again.
So yeah... my choices would be:
RE4 wii, zelda TP, and then mario kart to balance out the other 2 games.