There's no real "best lens" for wedding. It's how you use it and what you want to achieve. Some wedding photogs I've seen used any of the following:
- 17-55
- 24-70
- 70-200 (yes, this can work wonderfully too, if you think through the shot)
- 50 prime
- 85 prime
Some ppl think that close up shots are the best, which isn't always wrong, but you don't necessarily have to be close up to get close shots.
Some ppl think that posed shots are the best. This is not necessarily true and there are some who swear against it - especially if its not for the photoshoot album. For church ceremonies, fetching bride tea-ceremony, lunch buffet, dinner reception, dinner itself, candid shots can be the most powerful.
Check out the latest Practical Photography (or was it Amatuer Photography... can't remember), there's a good coverage on wedding photography.