There's LOTS of different ways for kids to learn to read! My oldest was taught through Direct Instruction (DISTAR), my youngest I took a more relaxed approach and simply read to him, listened to books on tape with him, sounded out words in front of him, left magnetic letters on the fridge.....
Kids get reading when they are ready. If they aren't ready, it can cause some serious problems by pushing it on them too early. If you do take your son out of school, I suggest not pushing the reading issue at all for the rest of this year but giving it a break and working on other subjects. I know Waldorf and (I think) Charlotte Mason type curriculums don't push reading before age seven, so looking at their structure might help you.
About possible medical issues, do take him to a doctor. Sometimes having that diagnosis in your hand helps more than you realize. You don't have to medicate if you don't want to, but at least knowing what is going on gives you the option to find out more and the many ways of helping without medication. If your son does have autism, there's no meds that would help anyway. My son is an aspie, and the few things that did help him were sessions on learning to read people's faces and body language, and removing certain foods from his diet (like dairy). Anyhow, by learning more about who he was, I could find more ways to help him, and that was a godsend.
You say your son likes to play video games. Have you checked out www.starfall.com