Fortress 2.
Ghostbusters 2.
Crank 2.
BATTLE ROYALE 2.
Alien franchise after Aliens.
Scream franchise after #2.
I know what you did last summer 3.
American Ninja 3 and beyond.
Saw past #2.
Critters 3 & 4...hell maybe even 2...has been a while.
Home Alone 3 and beyond.
The Neverending Story - 2 was bad, 3 was worse.
American Pie 2. Though I didn't mind 3. 4 was so-so.
The latest 2 "Universal Soldier" movies.
Terminator 3.
Harold and Kumar 3.
Friday 3
Lost Boys sequels.
Cube 2: Hypercube
Childs Play post-3.
Transformers 2. Though I didn't really like #1 either. 3 I enjoyed.
Hellraiser post-3.

...and from what I mostly hear "Grease 2".

Probably so many more....

Yep, they put a lot of thought into Howling III. Marsupials since it was made in Australia. The name of the town is "FLOW" which is "WOLF" spelled backwards, etc. etc. It had all the elements to be a comedy, but it wasn't. I like "bad" movies, but Howling III is painful to watch at best. I recommend it to friends with insomnia, 20 minutes in and you'll be fast asleep because even the most active of brains can't handle that level of boredom without dozing off.

Oh poor Alien 3. It had everything going against it. David Fincher did a brilliant job with what he had, but it was like Michelangelo carving David out of shit. I liked the return to the claustrophobia, and everything felt dangerous. The twist of having Ripley infected was perfect at that point. The writers and development hell had painted them into a corner so they had no choice but to end it that way.

For me:
The Mummy 2 took the over the top from the first one and just made it stupid.
With the exception of Nolan's Batman movies, I hate any sequel that replaces key characters with actors different from the originals. Like the Crow 2.

The 2nd and 3rd Tremors undid what made the original work.
The Saw movies beyond 2
Any Highlander after the original
The New Testament - Jesus really really pussified the narrative with all that love and understanding shit. That god would never have destroyed Sodom and Gomorrah let alone turn an innocent woman into a pillar of salt for looking over her shoulder. (I'm kidding)

All of the the howling sequels, And all of the crow sequels.

Chinese Ghost Story 2, and also 3. Somehow these sequels managed to be very uninvolving. Not without moments, but moments are not enough, I figure...

LOL! Grease 2...

Thanks a lot, cheebacheeba, I had blissfully forgotten about that movie till now! I know it had Edward Sissorhands in it, and most, or all, of the music sucked. But besides that, I don't remember if I ever actually saw it. I don't know if I could stand watching it.

Ghostbusters 2 was a big letdown. I saw it for the 2nd time recently, some 20yrs later. It wasn't as bad as I remembered, thanks to the cast (McNichol), it was mildly entertaining.

Some games also came to mind...

Resident evil 4 & beyond. Do not dig that perspective.

Ghoul Patrol.

Resistance 2 (cept for the multiplayer)

Fade to (fucking) black.

Sonic 2 - The master system version

Saints Row 3, and 4.

Dark Knight Rises. (The only movie where I actually asked the manager for my money back.)

X-Men The Last Stand

Kingdom of the Crystal Skull

Machete Kills

Son of the Mask

Dumb and Dumberer: When Harry Met Lloyd

Speed 2: Cruise Control

Superman III, Superman IV: The Quest for Peace and Superman Returns

Matrix Revolutions

Bourne Ultimatum

Spider-Man 3

The Hangover 3

Rocky V

2 Fast 2 Furious

Alien 3

Crow: City of Angels

Mortal Kombat: Annihilation

All Highlander Sequels

All The Howling Sequels

Just to name a few.

Godzilla (2) Raids Again 1955
Exorcist II: The Heretic
Howling 2
Ghostbusters 2
Alien 3