+1 to everything said so far - especially bicycle commuting to work.
Riding is supposed to be fun. I loved it as a kid. I love it as an adult.
My situation is much like yours, Mike. I bought an expensive (to me) bike in 2008 and rode it for a while. At first I couldn't get too many miles in and I was Slllllllooooooowwwwwww. It didn't take long, though, and I was making noticeable gains in speed and distance.
Then I met a woman, got married and got lazy. The bike resided in a forgotten corner of the house.
I recently dusted it off and started riding again. I've only been back on it for about two months now, but I've lost some weight (12 pounds at last count), lowered my resting heart rate and my blood pressure, and I feel pretty darned good. My wife is jealous. She says "You're getting skinny!" That's a bit of an exaggeration - I'm a long way from skinny - but the body reshaping can be seen.
Most of my riding is commuting to work. It's a 40 mile round trip. I had to build up to that. I started out riding to a bus stop @ the mid point and riding the bus the remainder of the distance. Once that became easy I found a route that I judged "safe" (traffic-wise) and started going the distance. Then I started challenging myself to do it more quickly. Last night I made 20 miles in 1 hr, 34 min - my personal best (without a tailwind).
Another benefit of riding is No Road Rage! I'm saving tubs o' dough in fuel cost. I feel great!
I guess I went through all of that to say this:
Stick With It! It gets better. Don't worry about what you can't do right now. Just ride for the sheer pleasure of it. Set small goals for yourself - even if it's nothing more than "I think I'll see if I can go one block further today". Like most things, all it takes is time and practice.
Very soon you'll find yourself saying "Wow! I can't believe I did that. I remember when I couldn't get .5 miles without getting out of breath!"
No get in your bike and ride, hombre! We're all pulling for you!