Van Helsing - I'd like to see Robert Carlyle for that. Or maybe Jean Reno. Someone tough who's not a pretty face and seems not entirely safe to be around, because he needs to be the flip-side of the Dracula coin, if you like. Jack Nicholson might have been able to do it before he became a self-parody.
Dracula - hmm. I think Gary Oldman could have done a better job if Coppolla hadn't stuck him with that script and "look". Or Alan Rickman, naturally.