The curse of the Sequels

In the film industry one of the hardest things to pull off is the sequel. The sequel is the key to having a movie franchise and a money making bonfire of profit that makes any film maker able to pay off the house notes. Though pulling off a good sequel is a lot harder than it seems. A good sequel needs to have a good flowing plot from the previous film to the newer film. The directing style has to match the old style and above all the cast has to remain constant through out the franchise or the true fans of the franchise feel cheated.
Now for examples. The classic sequel blunder I can point out is the Highlander franchise, more namely the first three films. The first film highlights the immortals as mystical beings who are more magical and mysterious. The film concludes with the Highlander earning the "prize" or the ultimate gift by killing the last immortal. But wait! In the second film, with the second director, turns out the immortals are not mystical creatures but aliens from another world and as it turns out the Highlander didn't get the ultimate prize because more aliens from his home world just show up and ruin everything. This film also takes place in the future after the highlander's company ruins the atmosphere, but don't worry by the end of the film all is saved. But wait there's more! In the third film not only are the aliens dropped but the entire future plot is dropped as well and guess what, the Highlander still hasn't killed the last immortal because there were several others immortals frozen in a cave far off.
Confused? Well so was the audience, and thus the ultimate failure of the franchise.
Now with some modern films that are bound to blunder and fall into the curse of the Sequels. Remember the X Men franchise? Well now were reaching back to do a couple of prequels, one dealing with Wolverine, and one dealing with the "First Class". What's the problem here? Well with both films heading in opposite directions, both directors are aiming to drop little lines here and there and have characters from the main franchise, like Professor X, appear here and there and offer little bits to link back to the main franchise. What's the matter with that? Well the more bits you throw out, the more plot holes you risk falling in. Like Saber Tooth nearly killing Cyclops, but then in the main film Cyclops has no idea who Saber Tooth is, and it probably doesn't help that Saber Tooth isn't played by the same actor in both films.
Or how about Iron Man, who suits up in his mechanical wonder to fight for truth justice and booze. With is trusty side kick War Machine, played by Terrance Howard (No wait Don Cheadle), Robert Downey Jr looks to cash in a load of money while ignoring the slight aggravation of fans at the change of War Machine. Let's hope the fans of the upcoming Avenger film aren't too fickle because early forecasts have revealed that Edward Norton will not take up his role as the Hulk again, it's rumored to have gone to Mark Ruffalo, and might I bring up both of these changes were made by the production company not the directors.
So now the big question is how will Transformers will hold out with this new sequel coming up. Early reports are the love interest of Megan Fox is out and is being replaced. The plot? Major holes, the newest trailer highlights that these never before seen machines have really been seen in 1969 by the Apollo 11 crew. Does this make sense? Nope. Early fingers are pointed down for this major film, and sadly for fans anger has already been stoked by a second film that's pretty bad on its own. So what's the lesson learned here? CGI, a good male lead and a beautiful but dumb female lead doesn't really add up to a hit film.
So what's the lesson learned?
If a sequel is to be had the for god's sake let's go that extra mile to make sure that it's a good one. Let's not be a Spiderman with out a Tobey Maguire.

Thanks All
J.