Ok, for my little trip down memory lane, I've owned:
Magnavox Odyssey - Membrane keyboard, completely pixelated graphics, few colors, and a joke of a cartridge which purported to teach one how to program, though the machine lacked any possible way to actually save any program you had entered when the power went off.
Apple II+ - My first "real" computer, which I originally had only a green screen monitor for, along with a single 5-1/4" disk drive. With the 16K ram expansion I bought along with it, it had a whopping 64K of memory, and I couldn't imagine for the life of me how anybody could ever need any more than that.
Atari 800XL - Picked this up because I had once had a roommate who owned one, and thought it was a fun little machine. Graphics and sound were better than the Apple II+ which had since acquired a color monitor, though the OS itself had a rather clunky feeling to it.
Atari 130XE - Picked this one up simply because it was cheap, had twice the memory of my 800XL, and had a higher density floppy drive than what I had on my older Atari.
Amiga 500 - Now we're talking serious computing. Since my Apple II+ still had been considered my "main" machine, this was a huge upgrade. Had considered either the Apple IIGS or the Atari ST, but once I'd actually seen an Amiga in action, I couldn't possibly have settled for either of those.
Atari Lynx - Hated the original Gameboy's lousy display, but loved the idea of a good handheld. With a backlit display, this was the logical choice, and knowing that a few of the Amiga's designers had been involved in it's design helped seal the deal for me.
Amiga 1000 - Had a friend who worked at my local Amiga dealer (the same one that sold me the A500), and when the dealers started accepting A1000's for discounts on A2000's, was able to pick up one of the ones traded in for $250, which seemed an absolute steal. I figured this one had to be a classic, if ever there was one.
IBM PC/XT - Ack! A machine representing the evil empire? Would have never bought this except for the fact that the price used was rock bottom, and I wanted to get a peek at a few games that could only be found on the PC. Upgraded the CPU with an oddball 286 card, which brought the speed up to 12 MHZ, and that made it barely tolerable when playing some games.
Super Nintendo - A nice machine for playing a few mindless games on, with nice graphics and sound capabilities for the time.
Sega Genesis - Bought 2nd hand, and while the graphics were fairly nice at the time, never really did care that much for it.
386/40 - By the time I got this, the PC compatibles had pretty well taken over the world, and I figured if I was going to be able to play any of the newer games, this was the way to go. I picked this one up from a friend and quickly discovered that this machine was still not enough, so gutted it's innards, upgrading it to a 486/66.
PIII/500 - After finally tiring of trying to find games in the bargain bins that would run on my 486/66, I finally broke down and built this one from scratch about 2 years ago. It was definitely a different experience going out and hand picking all of the components that I wanted to put in the system, and I'd highly recommend it to anybody who may be thinking of doing something similar. So far it's still been able to run everything I've thrown at it with no problems, so hopefully it's still got a few good years left in it. When it can't cut it anymore though, I'm sure I'll get a kick out of building a newer one.