Here is the thing with Doom 64, it was a completely new, built from the ground up Doom made exclusively for N64. It has grown a cult following for sure, with many modders keeping it alive on the PC with custom graphic mods. Some people call it Doom 2.5. I enjoyed it on the N64 but never beat it.
If your a Doom fan that just has to play all the Dooms, then you would have to play this one to say you've played them all.