I mostly play GT5, and just started getting into 6 a few months ago. Because I like going fast, but like taking these games slowwwww. In fact, I spent about a year with the first game, three years with GT2, not too long with GT3, maybe four years with GT4, but GT5 holds the record at 8 years and counting.
No interest in Sport.
GT7? We'll see. I'm mostly waiting to see if it'll be on PS4 or whatever the next console is. I don't want to get a PS4 then be stuck with not enough justification for spending that money.