If I'm honest mate, I'm open to going to any of the sports as at some point or other have had some sort of interest in them. However out of the four I'd say Baseball would probably be last on my list. Looking most likely Ice Hockey and Basketball with the time we're now looking at.
I was only joking of course... if you are not really into baseball, then going to a game can very possibly bore the hell out of you... unless you're lucky to watch a particularly entertaining one.
I'm a baseball fan though so I'd love to experience going to a game... will certainly do that when I'm in the US.
I don't think baseball tickets are expensive at all, unless we're talking about post-season games. Each team has 162 games (81 at home) in the regular season so I highly doubt an individual ticket would be expensive, though prices may vary according to opposition (a game vs the Padres is probably cheaper than one vs the Yankees, I'd guess)