Episode IV is the first part made, doesn't count, but the 4th Star Wars movie that was released in 1999 was pretty bad.

Indy 4 was shit.

Monkey Island 4 was disappointing.

Alien 4 was so bad it almost caused mass suicides.

Terminator 4 was a masterpiece deserving of awards and praise in comparison to T3, but it still sucked.

Fourth season of the reimagined Battlestar Galactica sucked (3 crying Adamas out of 89 crying Adamas).

Fourth season of Lost was pretty good.

The fourth Star Trek series, Voyager, is generally considered to be a pretty bad show.

The fourth time with Fink's mom was bliss.

The fourth of the 90's Batman movie series was impressively bad.