???
If anything Fo3 is the odd one out. I don't get this statement at all.
Fallout 3, have the super mutants and Enclave as main enemies, water and geck are important for the main quest.
Fallout 1, super mutants are the main enemy and water is the important main quest.
Fallout 2, Enclave is the main enemy and geck is the important main quest.
Fallout 1, start as a vault born.
Fallout 3, start as a vault born.