Both are correctAssuming you're specifically interested in talking about television, but they would refer(as opposed to different conceptswhether one uses plural or singular nouns after "two kinds of" in general), it depends on context.
"Two kinds of televisions" would refer to different kinds of television sets, as in "We have two kinds of televisions: color and black-and-white."
"Two kinds of television" could refer to different kinds of televised programming, as in, "Programming for kids and programming for adults are two kinds of television."
Compare countable and uncountable definitions of television on wiktionary.