Things that shouldn't have been in the games.

That giant blue automatic scythe, for one. By now I've forgotten what it's actually called. It looks like a Queen, or something... I think.

The Ravager? Those things were whacked but for gameplay purposes they kind of made sense, but if you think theoretically, the evolutionary need for such a creature is restricted to if the hive is against something that cannot be impregnated.
The Carriers, on the other hand, would make much more sense.

Personally I think everything that's been in the games, in context, has made sense. Although I do agree, the Ravagers could have been left out of it.

All the ridiculous sub-alien species they made up to pad out the games.

Keep it cannon or I don't want to know.

I think the xenoborgs in AvP1 were pretty useless, and easy to beat, even though they were presented as some sort of high level threat. Could have been replaced with more predators or something.

Here's the thing about games-If you don't want to fight the same enemies over and over again, they've got to make a few more types of aliens. Ravagers would be idiotic in a movie, but the role they played in Extinction made sense.

Some of the sub-species were pretty rediculous.

more levels >.< and a new AVP extinction game (i kinda love that game)