In the original movie he was pretty messed up since his kid had recently shot himself. So he was pretty wary around guns and freaked out when Skarra even got close to one.
Then in SG1 he starts hosing stuff down and handing out weapons to various resistance people and the like.
And Superman Returns technically WAS a (failed) reboot of the series, by the way :p
As for Batman: Nolan basically DID ignore every single live-action Batman that had previously occurred (took more inspiration from TAS and comics, really). And it really helped. The Batman mythos didn't change too much, just the interpretation of it.
As for Ultimate U: That is kind of why I clarified "first year or so". From what I gathered, most people found it to be interesting, but maybe not amazing. That being said, it kind of did get a much smaller fanbase after that first year or so when it started doing actual storylines :p. For the record, I also hated Gak-Lak-Tus and only read it for USM at this point.
I am not saying that a few bad sequels really justify making a crappy game. Nothing justifies making a crappy game. But we don't know that this is a crappy game yet.
Here is what I am saying (I either outline it, or yell at people and accuse them of not listening. I like the fun way :p). All of these points are independent.
2K-com (let's hope that catches on) is a reboot of the series. If it is more reboot or reformat, we don't know. That is okay and expected. To continue on with a sequel would deal with Interceptor and Enforcer. We don't want that.
As long as the core gameplay/core elements/core style is maintained, I don't think the majority of fans would complain (outside of the ones who will complain no matter what). Because as RPS put it, XCOM is the gameplay, not the plot and spriteset.
2k-com acts as a prequel to the XCOM games. It takes place during the first contact era and focuses on the foundation of XCOM. As such, it focuses on the US (it could just as easily focus on Britain or Russia)
This in and of itself is not a bad thing. It provides a way to provide modernized gameplay. As much as we are okay with that style of gameplay, do you see it being accepted by most modern gamers? As such, an emphasis on smaller scaled gameplay is probably for the best.
Keep in mind that when I say "modernized gameplay" I don't mean making it an FPS (that is the next bullet point :p). I mean making it more accessible to new players (even just providing a more gently sloped difficulty curve), lessening the emphasis on "Research or Die!", or providing stronger recruits (just considering that almost everyone would be a veteran of WWII/Korea/Vietnam would give an excuse to provide an easier start).
2k-com is an FPS (at least as far as tactical gameplay goes). This is a pretty big concern and pretty much guarantees that we aren't getting a clone of XCOM. But that is still workable. I feel that I already provided examples of very tactical (and unforgiving) games with an FPS/TPS perspective already. Beyond that, it is just a matter of getting the atmo right.
So while this does mean that we won't get XCOM 4 (because there were only 3 true XCOMs :p), that doesn't mean we won't get an XCOM game. Think of Fallout 3. Is it as good as Fallout 2? Nah, although I suspect I also am seeing things through rose-tinted glasses. But is it still a Fallout? Yeah. It is just a different kind of Fallout.
Individually, none of those are really a huge problem or a destruction of the series. Now, together it starts to get very scary. But maybe we'll all be wrong and they will get it right. At least wait before jumping to a conclusion. At the very least, it will make it much more satisfying when we are probably proven right and it is a horrifyingly blasphemous game. And wouldn't you like to at least have the comfort of saying "I tried to give it a chance, but they just kept insisting on raping me in the butt with an aluminum XMas tree" while we cry over yet another crappy game with the XCOM name? :p