Not OCD, but I sometimes tend to go OCPD on games sometimes. I always have to pick up that heart or rupee even when I don't need it. Or backtrack once I reach the end of a level to make sure I didn't miss anything. Or always add skill points to my character in multiples of 5. Or save right before making a decision so I can go back and try the other options until I find the one that's the best.
This. If I don't explore a whole level or area; I will always have that on the back of my mind. I might reload saves just to check. This happens a lot in games which forces you to continue the story when there isn't a clear line where the level ends.
Humans naturally like things "to fit" per se. You don't have OCD until it gets in the way of life. That said, I do a lot of OCD-like things in games. LoZ games I had to pickup any drops even if my health and/or wallet was full. In shooters, I have to reload when I'm safe even if I've only fired one or two shots. My TV volume and other slider settings like sensitivity have to be on an increment of 5. And so on. Of course, it doesn't kill me if I don't do any of these things.
I don't think 90% of the general public really has any idea what OCD is...
I can't speak for other people, but for me, OCD has always been about intrusive thoughts and irrational fears. It's like having another person living in your head, who's sole purpose is to feed you shock images and thoughts, or just generally harass you. The inability to control it is frustrating, and the thoughts and images leave you confused and unsure of who you really are sometimes.
Just cause you like to complete games 100% doesn't mean OCD. I used to care about compleing games 100% more when I was younger. As I age, I care less. I play a game and ejoy it. If I really liked it I will replay and may go out of my way for extra achievements but that's about it.