I7-720qm, is 73C while gaming ok?

That's about right. Laptop CPU's have a much higher thermal envelope (i.e. the temps they can take) in comparison to desktop cpu's. Just ensure that you have the laptop on a flat surface like a table or hard cover book when playing a game to keep it cool as possible.

Agree. Your machine is fine. Start worrying when it gets into the upper 80's.

Niceone thx guys you have set my mind at ease.

The mass market 720QM laptops have a very tight thermal / power envelope. You will notice for example over on newegg that there are 23 720QM machines there are no 820QM's. That is because both the power supply and the thermal management system are pretty much at their upset limit with the 720. Based upon calls I have made inquiring about the 820 option, the 820 / 920 are officially options on many of these machines, many vendors have backed off selling it for this reason.