Personally I'm not a fan of Twenty20, having been a cricket fan since I was young I grew up watching test matches, so it just feels like an Americanisation of a more traditional sport.

Slightly ironic given I'm actually a bigger fan of baseball than cricket now, but my order of preference would go baseball > test match > twenty20.

Side-question: What country are you from, i.e. where does your interest in cricket come from?