I don't have a problem with most shooters or the types of games I'm interested in. It's stuff like sims, sports and puzzle games that I have a hard time staying focused on long enough to get good at them. I'd just rather spend my time on games that are fun for me without having to try to get into it.
That's what I like about most Neo Geo and arcade games. They're made to draw you in fast and are easy to get into. If I was still in high school and had the summer off, I'd play a lot more of the kinds of games I'm not crazy about. But the older I get, the more valuable my free time becomes.
Shooters may have a lot of variety, but they really benefit from playing off of the same skills you learn from each game. I also played every one I could bitd, so I find the genre pretty easy compared to others. I never feel like I have to 'get into the zone' with shooters, because I'm always as in as I'm going to be.