Your problem is, that the gate of an N-ch. MOSFET needs to have its gate-pin positive a certain voltage in respect to the source-pin to open (in case of the IRF540, slightly over 4.5V) to open.
Also, if you look at it dynamically, you need to supply a good bit of current, to the gate to get it through the Miller plateau in a short time - 71 nC (nano-Coulomb) needs to be filled into the ~2nF input capacitance, when using the IRF540.
Simulators often give you false results. In a real life circuit, you'd probably get less than about 1V.
To get 12V, you need around 17V on the gate of Q1 and if you want it to do anything usefull, you need to lower the gate resistors considerably.
For a discreet build of an H-bridge to work without the gate voltages above the main circuit voltage, you need to use P-ch. MOSFETS.