I think history is being very kind to Terry but Ferdinand was an absolutely imperious defender - a genuine all-time great imo. VVD has got a lot of career left and a lot of trophies to win before he can claim to be better imho.
Leaving aside what an absolute prick the bloke is off the pitch, it shouldn't be forgotten what a magnificent defender John Terry was. He was so dominant. Ferdinand was brilliant too, but from a pure defensive point of view, I think Terry was better. It's a massive compliment for Van Dijk to be compared to either of the two, but you're right - we'll see how his career stacks up to theirs at the end of it.
Edit: God, England were spoiled with defenders in the 2000s. Terry, Ferdinand, Campbell, Carragher, Neville, Cole...