The basic plots for the AVP films weren't necessarily bad...

It was the setting. Setting the two AVP films on present day Earth was a MASSIVE mistake.

Like the title states, the plots (particularly the first one's) weren't exactly bad--in fact, the first AVP's story could have worked extremely well had it been set in the distant future on an uncharted planet. The plot could have been roughly the same (minus the whole "Predators were treated as gods by humans" idea): the Weyland-Yutani Corporation (and the Colonial Marines) intercept a strange signal from a planet that was thought to be uninhabited. The Weyland-Yutani Corporation use this as an opportunity to fuel their greed and potentially build their bioweapons arsenal, while the Colonial Marines believe that the signal may be a call for help from humans stranded on the planet. Both factions race to the planet to investigate the message's true origins, only to find that it was a trap set by the Predators to lure hosts (and prey) to the pyramid. As the Aliens' numbers grow (and Weyland-Yutani's true intentions surface), an all-out war ensues between the Colonial Marines, Weyland-Yutani, the Aliens and the Predators.

The sequel could have, again, been fairly similar to what we were given. The Predator ship carrying the infected Predator could once again crash land, this time on a colony owned by the Corporation. Wolf would show up to "clean up" the mess, with the humans living in the colony caught in the crossfire. The humans believe that the Corporation would come to their aid, but given Weyland-Yutani's true nature, that is obviously not the case. At the end, the infestation becomes uncontainable, and Wolf sets off a nuke to obliterate the colony before the Corporation has the chance to obtain any Alien specimens.

If better actors were procured, hard R-ratings were given to each film and better writers and directors were attached, I think these could have been two very entertaining, memorable and worthy movies. While the actual stories were subpar at best (especially Requiem's, which I felt was downright terrible), the ideas behind them certainly could have worked had they been incorporated into a different setting altogether.