MerricB said:
MageKnight was great because it was the first CMG. Unlike Magic, however, it couldn't sustain itself. It really carved out its own niche with its selection of miniatures - but that left it vulnerable to DDM, because role-players wouldn't find much useful in MageKnight.
Personally, I found the MK minis to be as useful, if not more, for D&D than the D&D Minis line.
When MK first came out, I bought up a fair supply of MK minis, since they were cheaper than metal minis and the DDM line hadn't been created yet. It would probably make MK collectors wince, but I popped the MK minis off their bases (most came off very easily) and glued them to a normal 1-inch base. On the secondary market, bulk MK minis are dirt cheap, I bought 200 of them on eBay for $40, and most of those were pretty usable for D&D (a few steampunk creations aside), but it was a great deal for just having lots of humans/elves/orcs/generic monsters/undead. By the time the D&D minis line came out, I had most of the minis I'd need to run a game, and the D&D minis were more expensive, and much more expensive in the secondary markets.
I think that part of MK's problem with fading was that they started adding a lot to the system. Part of MK's appeal early on was that it was a fairly simple game, with one list of powers and all you'd need to know would be on the mini. Then came spells, and artifacts, and the dungeons rules, and this and that, and it started being more like a collectable minis based RPG, and away from it's simple and quick to play roots.
MK also lost a lot of steam when its fad faded. I noticed something very interesting in the demographics I saw at MK tournaments at my FLGS when it first came out and was very big. About half the players were young kids who were into the "next big thing" after Pokemon had passed it's prime and MK was jockeying for some of that market. This meant you had a lot of kids buying with reckless abandon with their allowances. The rest of the people I saw at the tournaments were about evenly divided among gamers who were interested in the whole "collectable minis game" idea and were dabbling in it (and maybe picking up a few boxes for D&D), or among middle-aged gruff-looking wargamers who played the game and griped incessantly that the minis were plastic and prepainted and the rules were too simple (and plenty of offhand comments about how 40K is superior, all real minis are metal, yadda yadda. . .) Over time, it looks like the wargamers went back to GW, the gamers who were dabbling or buying for RPG"s went to D&D minis, and most of the kids moved on to Yu-Gi-Oh cards pretty quickly.
WizKids created the entire genre of CMG, and carved out a niche where none was before, but it doesn't look like they were exceptionally good at holding their position.