Generally, get the bike that suits where you are riding. A road bike will be the most comfortable for long rides (even though they seem awkward at first). If your routes are too rough for a road bike, get a hybrid, and if they are too rough for that, get a mountain bike.
Cruisers and other "comfort" bikes are only comfortable for a short ride. For longer rides, you'll want your weight split between pedals, handlebars, and the seat.
Personally, I had a mountain bike and almost got a hybrid because it was closer to what I'm familiar with. After getting the road bike, I only ride the mountain bike when necessary. I find the road bike much more pleasant to ride if I am staying on pavement.