With regards specifically to homosexuality, the bible states it is a sin. Humans are generally happy living in sin. (Liars, thieves, adulterers, blasphemers, etc). My understanding of sin is that it is all basically equal, which is why I mention the other more obvious forms. Additionally, in some cases, it is accurate to compare, specifically kleptomaniacs (who claim it's not a choice to be that way), et al.
Also, using a general statement such as "gay people are happy being gay" is a gross misstatement. Most homosexuals I've met are hardly happy, much the same as most heterosexuals. In fact, I'd venture to say most homosexuals are less happy, just because of the stigma they face for their lifestyle.
Since you claim you're not a Christian, it's obvious that you're not sincerely interested in this question, so I will close this topic. You can post on the PaRD if you have any further such questions that you want like-minded answers for.