Well, that being said, vGBX covers the GB and GBC because they share a similar platform. Most of the hardware is the same, and the GBC is backwards compatible. The GBC is essentially a Game Boy with 4x the RAM, 2x the Processing speed, and a color screen.
If, for example, I was to do a Sega Master System website, it would also include Sega Game Gear games, because the only difference is a slightly modified PPU in the Game Gear that shows more colors at a lower resolution. The rest of the hardware is basically the same between the two.
The Atari 5200 and 2600 don't share that sort of relationship - they aren't backwards-compatible, they aren't even really a similar system.