I’d agree that the overtaking in bike racing isnt as exciting – they’re almost always done under braking for a slow corner, defending is pretty much non existant and theres moves every lap. The real excitement in it comes from the battles, with different riders counter attacking or pressuring the guy in front until he bins it (which happens surprisingly often).
Take the battle between Rossi at Lorenzo at Catalunya in 2009 http://www.youtube.com/watch?v=NfL52GliW9o (if only F1 races there were that exciting)
Or my favourite, the battle between Rossi, Kenny Roberts Jr. and Toni Elias at Estoril in 2006. http://www.livevideo.com/video/23C5CA7199E34677A3C4E36C1106652D/last-lap-motogp-estoril-port.aspx
I understand it’s not for everyone but there are a lot of genuinely exciting races every year (though the 2010 MotoGP season was very dull).