Yes Bitcoin is the most gambled, and Ethereum is next.
I have a crapload of monero which I like as a coin, but it's a small % of the gambled coins. Would it be prudent to trade some monero for say litecoin or something?
Not sure if this is the right place to ask this. But generally if you are holding something just for gambling, what's the point of exchanging it? You can just keep it and gamble with it on the site that accepts XMR as a coin to gamble with. Well I think there are a lot of gambling sites that accepts this coin to play with, like fortune jack. Also, be mindful that if you exchange your coin to something else, there are fees involved. So just avoid exchanging it.