Capcom Versus has, so far, included the following franchises:
There has also been another Capcom crossover game - Namco × Capcom, which is a lesser known RPG which was done in conjunction with Namco.
Marvel vs. Capcom Series
Marvel vs. Capcom is a series of fighting games developed by Capcom in which characters created by Capcom and Marvel Comics were put together to battle it out.
The Marvel characters depicted in these games were mostly based upon their incarnations in several early 90s cartoons (predominantly X-Men), and were often voiced by the same voice actors as in the animated series.
Many of the characters and gameplay tropes used in the series were initially created and refined in two other fighting games Capcom had previously made. These games ( X-Men: Children of the Atom, and Marvel Super Heroes) can be seen as precursors to the main series.
Although the tag-team fighting model wasn’t an original concept, it was refined with this series (although fans would debate whether this was for better or for worse).
SNK vs. Capcom Series
The SNK vs. Capcom (or alternately Capcom vs. SNK) franchise is a series of games in which characters from Capcom and SNK games cross-over
The reason behind the differences of which companies name comes first in the title is that the company which developed the game got to put their name first.