Well, I'm sure I'll catch flak for it. But the Amiga, the 1000, and to a lesser extent the 500. Both were majorly disappointing to me because I kept hearing about (from computer salesmen) and reading about (in magazines) how great the Amiga architecture was, how it was the last word in graphics and sound.
So I bought into the 1000, and it sat on my desktop, doing little and accomplishing nothing. I had it for a couple of weeks before I returned it to Farnsworth, minus $100 for a restocking fee. I bought some remote control cars and other stuff with the money. It was something like around 1200 or 1400 bucks.
A year or so later I got into the 500. And initially it sat on the floor in my bedroom. I, like a fool, had been blabbing about it to my buddies. And when the rubber hit the road and everyone wanted to come see the state-of-the-art arcade games and graphics, I had little to show except for a couple of non-interactive animations and what came with the Amiga Basic and WorkBench disks. Not very impressive. No arcade games to be found. No computer store stocked anything.
Later on they did stock some things. And I partly redeemed myself in the eyes of a few friends. But mostly it was a bust for game playing. Again the salespeople lied.
Personally, myself, I did discover PhotonPaint and how to play with hi-res pictures. I drew some porn and collected even more of it. I also drew some Sci-Fi stuff - which I still have saved today. It was a respectable intro to graphics and digitizing with Digi-View.
But overall, the system was sluggish and never lived up to the ideas swirling in my head. There was nothing to generate procedural graphics. And Jet and Flight Simulator II were marginally better than what was available on my 1MHz Apple II. So that was a flop.
Soon the PC and the 486 came into my sphere of awareness and that rig matched my expectations for something speedy and snappy. A fast hard disk, no more grinding floppies except on installation of new software. And as time went on the graphics kept getting better culminating with Duke 3D, Doom, Raptor, Whacky Wheels, and others. Even fractal rendering and astronomy software was available. And I didn't even have a hi-powered graphics card yet. Just a budget CL5422. And then there was PaintShop Pro. So yeh.. I had little use for the Amiga as the PC was proving superior in every respect, cost aside. But what good is cheap hardware if all it does is frustrate you?
Most people will complain and lay hate on me. Eh.. whatever.. Remember, it's not necessarily the hardware at fault, but how it was marketed, the expectations put in my head by that marketing.. That sort of thing.
As far as disappointing consoles? I would say the disappointments were minor and like a few bumps, but nothing to turn me away from the platform. Odyssey^2 adverts were getting wordy at times, but I took it for what it was worth. Astrocade was unreliable, but more than made up for it with real arcade sound once I got a working unit. There were of course many crap filler VCS games, but that wasn't a reflection on the console itself. The 5200, being a repackaged 8-bit 400/800 computer was disappointing, but yet, to a kid, there was some futurism and mystery surrounding the console and that kept in my sphere of interest. Intellivision had funky controls..
It was all small stuff. And more like quirks instead of bombing disappointments like the Amiga.
Now, as far as good experiences go. I'd have to say all the early 8-bit consoles. The Apple II, the Atari 400/800, and even the C64 impressed me with the sound in its port of Gyruss. The Apple II was a remarkable learning platform for all things techie and layperson alike. I had THE best of times with the VCS and Apple II. And the 400/800 had some good arcade-like ports. All around it was a good time that seemed to fade when 16-bit came on the market. And the magic wouldn't return till the early 90's with PC games.