I agree, worst case scenario is the new title is horrible and flops, my opinion is who cares, I still got the classics that I love. Going through wc2 again as we speak.
Like a lot of people I can have my enjoyment spoiled by something sub-par.
The most obvious example of that is Aliens, one of my favourite movies, but knowing how Alien 3 starts spoils my enjoyment of the ending every time.
Alien 3 isn't a film I enjoy watching and its existence decreases my enjoyment of something I do love.
That's not to say that's inevitable; all the bad Terminator sequels in the world don't spoil my enjoyment of the originals as the premise is built on alternate timelines.
There are definitely sequels I'd rather not have, and circumstances where I'm more than happy with something that didn't live up to expectations.