I admit I make the same mistakes, buying games I don't really like, though not to such an extreme as you do it appears. I would never buy a racing game for instance because they simply do not interest me, but I did make the mistake of buying Force Unleashed simply because I thought the force powers would make the game fun (I was wrong). If a game has an interesting story or 'cool' gameplay mechanic then I will often buy them even if they are genres I don't really like. Oftentimes I will regret it but sometimes I do find a game within a disliked genre that I do like, for instance I don't normally like FPSs but I do love Half Life 2 (Half Life 1 was meh though, never really saw the appeal in that one), though maybe it's because I love the setting more than I hate the gameplay style.
As to supporting the industry, I will happily buy a indie game, they're cheap enough and good for a laugh. Big name titles though, I expect them to put some serious quality in them as I will not support some junk (I figure it's more harmful to allow poor quality products to thrive, since it gives those megacorps the wrong idea about what we'll accept), which has resulted in me finally deciding to no longer buy games at launch. DA2 I will buy when it's GOTY edition comes out, if I buy it at all, since apparently rushing out to buy it on launch just gets you buggy software and ingame salesmen (refering to DAO there).