I'm going to voice what may be a bit of a controversial opinion here on the escapist.
Simply put, sequels/clones are good, spur innovation and improve the industry.
Some points to think about
-If you liked, say the origional megaman, then one day while strolling through the store saw "megaman 2" you'd be pretty annoyed if you bought it, and it turned out to be completely different from the origional megaman in every way. When you buy a game with the number 2 on it, it is because you want to play more of the first game, maybe refined and touched up, but you still want the same core expeirience. True innovation of basic gameplay concepts should therefore only come from origional IPs.
-Creating origonal IP's takes alot of time and effort. You have to plan and have meetings and create a fictional world and characters, spend years creating all the art and visuals of the game, have dozens of people banging out code to get a working game running, then come the bug testing, the reworking of flawed ideas, bug checking, beta testing ect ect ect.
It takes so much work infact, that the game devs often run out of time and have to ship before they've made a game they are 100% happy about. Thus origional IP's often lack polish, are often buggier, and usually just all around worse than a sequel where they have half the development done already and can just focus on doing new and interesting things with the core concepts they've already worked out as FUN.
Perfect example, assasins creed. The IP started out with origional ideas and true gameplay innovations, the final product of this new IP was buggy and filled with numerous less than fun things that sould have been worked out (as ZP put it "a faffing about fetish" ). The sequel didn't come out with any major new ideas or concepts, but improved the core concepts and made what was established in the first game fun and refined.
Sequels are what spurs the little innnovations within gaming. Better GUI's, better graphics, better storytelling, better balance ect ect ect.
To use an art analogy, an origional IP is like a pencil sketch, crude and unrefined, but with the basics of new ideas. A sequel is the finished masterpiece that you can analyze for every trick or detail to use for your next painting.