Eye On Cricket makes a more than reasonable case that Chris Gayle did not mean what he said about the Test format:
I think he rates test cricket highly and takes it seriously. His expression after the win in Kingston over England earlier this year spoke volumes about what he thinks about tests. If you are a serious cricketer (and despite his hang ten demeanor, Gayle is a pretty serious cricketer, rest assured), you have to have figured out that test cricket is the highest form of the game and that winning a test is a big deal.
I agree, but I’d add one more possibility: perhaps, after playing for so long with a failing Test team, Gayle prefers the formats where West Indies have enjoyed more success (i.e. ODIs and Twenty20).