The ZX Spectrum is an 8-bit microcomputer that was released by Sinclair Research, Ltd. in 1982. While I think the Commodore looks better, the ZX Spectrum became the best selling computer in the United Kingdom (its home country), and so many clones were made of the computer that it probably outnumbers the number of Commodore 64s out there in the wild. One of the most important things that made it more attractive to consumers was Sinclair's preference of making things affordable.
The ZX Spectrum had amazing reach, with both official and unofficial clones pretty much everywhere. In the USSR, if you didn't have something like the Elektronika BK, you probably had a Spectrum clone. Like the Commodore, the Spectrum ran its own flavour of BASIC, introducing every user to computer programming. Almost every British game developer to have grown up in this era probably grew up with access to a Spectrum or one of its clones.
The ZX Spectrum is a computer I would like to get to know better. A lot of Spectrum emulators are very confusing to me, but that may be due to the C64 emulator I use (VICE) spoiling me. I'm also very interested in learning more about the various clones of the system—I will probably write a bit about a couple of them when I have the time.
The graphics of the ZX Spectrum's earlier models leave much to be desired. While a lot of the programs are very impressive, the ZX Spectrum ports of various games often feels crappier when compared to its competitors. The original ZX Spectrum only had 16 kilobytes of RAM, though there was a more expensive model that had 48 kilobytes (commonly just known as the 48K). The higher-end ZX Spectrums could have up to 128 kilobytes, and this model is often referred to as the 128K.
The ZX Spectrum itself only came with a beeper, but it was common for people to mod their systems to include an AY-3-8912 chip, which allowed for more sound (said AY chip was there by default in the 128K, and the model lacked a beeper). Despite the limitations of just a beeper, people like Tim Follin were able to achieve polyphony with some awful assembler wizardry. A program was actually written for him to be able to make music easier, and in more recent times a tracker for Windows has come about to make the process easier for people who likely can't read assembler. A good example of the possibilities of the beeper can be demonstrated by the works of the Russian artist shiru8bit.
Most games available for any other microcomputer would be available for the ZX Spectrum as well, and often were compatible between 48- and 128K versions of the computer. Most demoscene demonstrations I've seen use the 128K, and most games generally seem to feel better on the higher end Spectrums.
Many ports of arcade games were available on the system, such as Pac-Man and its various versions. There is also a very strong homebrew community who are able to make games that would potentially make an 80's era programmer faint. Regardless, there are very good games for the system regardless of what era you're looking at, and there's really impressive demos dating very far back, too.