I absolutely adored the work of Elmore, Caldwell, Brom, DiTerlizzi and Easley. So art in BECMI and 2e is my favourite. A great improvement from OD&D and AD&D 1e, IMO.
3e art was very good (Lockwood Dragons!), but overall less impressive.
Sadly, I found 4e art revolting, with exceptions.
5e art...