If you are redifeining the speed question to "the same thrust at two different altitudes" then the answer is easy - the aircraft at the higher level will be travelling faster because it will experience less drag, as the air density is lower. The resistance of a body travelling throught the air can be stated in the simplest form as:
R = K þ S V²
Where K would be the drag coefficient of the aircraft determined by experiement, þ the desity of the air, S the frontal area and V the velocity.
Now, as you originally stated your question:
If a jet is travelling at max power at sea level and an identical jet is doing the same at 37,000 ft which jet is going faster ?
Things become a little more difficult to answer, as the problem is complicated by other factors. A jet at sea level can produce up to ten times the thrust as a jet at altitude, so "flat chat" at sea level might mean 20,000 lbs of thrust per engine, while flat chat at the maximum altitude might mean 2,000 lbs of thrust per engine.
As
411A stated above, flat chat at sea level will quickly accelerate the jet past it's maximum speed - eventually bits may begin to fall off the airframe
but if you ignore this, then I imagine the sea level jet may be able to sqeak over the line in the outright speed stakes - although it would be destroyed in the process.