First if your internet company let you use two modems, you would have to pay for 2 accounts. Usually a cable modem has to be authorized for your account, so just plugging 2 in shouldn't give you a 2nd line.
Now bridging connections doesn't do anything for gaming as you still have two IP addresses. Bridging just speeds up surfing, and downloading mostly. You would still need a 3rd modem capable of bridging though.