There have been a lot of good points brought up. There's nothing that I would really disagree with. This is just more of how I dealt with the same issue.
I used the "Rule of X" approach for offense and defense. The biggest thing I did was limit how many points they got per session. Two was average and the 3rd point was for outstanding game or role-play. I also stated that offensive or defensive powers could only be increased every 3 games. Occasionally, if the team or a specific player developed a contact during game, that was what they got as XP. I never had anyone offended or upset that they were given something like that. I also made sure they had background skills. If someone said they were a physics professor at the local school, then they needed a couple of science skills, teaching professional skill, and possibly some local ks skills. I also made sure that I ran them in their secret Id's. They had to be able to function in their jobs and hobbies. I personally tend to always put in one oddball skill in my characters, even if its just a familiarity. It's a personality pick and I look for that on characters and make sure I reward it and bring it up at least once in a game somehow. Of course, YMMV.
Good luck.