Actually I don't see the sense in questions like this. Reminds me of these radio shows where listeners can vote for the top100 of the best songs of all times and then 90% of the top20 songs are not older than one or two years or are an actual top10 hit of the last few weeks. I think you have to see the design especially of computers in context with the esthetics of the time when it was released and what was technically possible at that time.
Today we find beige boxes ugly... in the late 80's that didn't bother anybody at all. It's a question of fashion and zeitgeist. Maybe wooden enclosures will be the next big think for computer manufacturers and we'll find the metal enclosures from today totally ugly! If we don't take that into account, the question doesn't make sense...
For example in my opinion the G5 case design is not bad compared to other enclosures on the market, but it is far from being beautiful. Especially the size I don't like, it's too big! I remember all the people complaining on this forum how ugly they were when they were introduced. After a while it grew on the people and now everybody thinks the G5 design is the holy grail. Maybe it is funtional... but beautiful? No, Sir!
There are four Apple enclosures that were really nice in context to their time:
1) SE/30
It was a really cool computer back then and any PC didn't come even close!
2) LC case
Small, functional, quite. THE incarnation of the perfect pizza box.
3) Quadra 840AV
I just love(d) the mini-tower design of that machine.
4) Quicksilver
The best looking enclosure of the "newer" Macs. I like it way better than the all aluminum design of the G5.
The Laptops are all OK. I don't have any favourite. The only ones I didn't like were the toilet seat iBooks. And the quality of the iBook enclosures in general wasn't exciting at all. Especially the G4 iBooks have a cheapness factor regarding the quality of the enclosures.
groovebuster