Bought a 5D mk2 : what lenses now ?

I bought a 5D mk2 this weekend. The story is i bought a second hand 5D mk1 first, but after a few days of testing, i returned it and went for the mk2. Allthow the 5D is good, the mk2 seems even better to me.

I now have an old analogic 24-85mm which seems not the sharpest lens on earth...!

I'm looking for a good all-round lens for the mk2. OK there is the 24-105, but aren't there any other like Sigma 24-70 that are recommendable ? The lens should be very sharp. Eventual i want even buy all primes.

Thank you for the help...