Remember all those times folks told you, "marriage is work"? Well, you're now faced with the "work" part.
First, forget what he did with the ex. You're in this for the long-haul now. Both of your tastes, preferences, hobbies, activities, etc, will change over the years.
You need to chat with him. Not nag, not complain, not whine; but a nice chat about computer/tv time. It's all about compromise. Make sure he knows he can chat with you, too, about anything that's bothering him.
There's all sorts of things couples can do. I, too, suffered from me watching tv while DH was glued to the 'puter. We compromised. I now make sure to rent something I know he'd like, too, from the video store. I also pull up a chair during his puter time and we check stuff out together, i.e., news, jokes, funny videos, etc. Heck, we've even gotten mildly addicted to a mindless computer game together
You both can sort of "allot" personal time for each other. For instance, I do most of the cooking for dinner. Hubby checks his 'puter stuff while I cook. He does cleanup after dinner while I check my 'puter stuff. That way, when dinner's over, it's "us" time.
Don't forget ... don't lose the spice in your marriage. This is something I wish someone had told me years ago. Get creative. Change things up. I can almost guarantee you that if you put on some sexy lingerie, put something, um, adult or some nice music on the tv and whisper for him to "come to join you," he'll get off that 'puter in a second!
Best of luck