Depends on what you call a sequel, there was no sequel to ATF(Advanced Tactical Fighters) though Janes´ Fighters Anthology looks too similar to not have the same engine, I think. If you say same engine, different name is a sequel, then Hidden and Dangerous 2 would be a sequel to Mafia.

Because that can´t be, I agree on Mafia.

And I really hope you´re not implying that all sequels were bad(don´t think so, just in case...)