From a aesthetic point-of-view the original 1000 looked great (very Mac like) and the 3000 tried to follow that design. The 2000/4000 just looked like bland boxes, not very interesting. Obviously the 500/1200 were a nice design for the budget.
Technically, the original 1000 and 500 were the best.....it was all downhill from there

My personal favorite Amiga's: A1200, CD32, A3000