There are nothing "same" about them except for the F. One is DOHC, high compression, forge internals, short stroke, high revving engine. The other is SOHC, low compression, cast internal, long stroke (torque for heavy chassis). The F20 also have some kinda fancy coating on their cyclinder wall. If you want to get technical, I'm very sure the bearing journals between the two engines are different sizes too.
The F in the Accord is kinda like "F this $hit", and the F in the S2000 is kinda like "F...ing hell yeah".