Bulldogs are known for their lazy, dull demeanors.
Many people who buy them want them for that reason - they like the bizarre look of them and don't really want the trouble of a dog with excercise needs.
Since you already have your dog - the best thing you can do is (in a calm fashion, please) start to encourage livelier behaviour by the following method.
1- Determine what would serve as a reward.
Observe your dog carefully and determine what he does like. Since most bulldogs are fattish, my guess is that he likes food.
2- Reward those behaviors you'd like to see more of.
This is tricky.
Suppose you'd like it if he was MUCH friendlier.
What you need to do is to notice any small amount of friendliness by rewarding body language that relates to friendliness. For instance if he happens to come into a room with visitors. Have the visitors toss his favorite treat to him.
Every time you see him take a small interest in something - reward.
Ignore him when he's dead to the world. You don't want to inadvertently reward antisocial behaviour.
Make him come to solicit dinner - this way you'll be encouraging him to take action (This is exactly the opposite of what you'd do with a hyperactive dog.)
Finally, don't expect huge improvements.
Make sure he isn't sick - and then accept him as he is.
(As long as he doesn't bite people).
Next time, get a different breed.
(Hint: avoid breeds with extreme physical characteristics.)
Best of luck!