I agree that neither
Star Trek XI nor
Superman Returns are actual reboots.
Star Trek has already done recasting. Robin Curtis replaced Kirstie Alley as Lt. Saavik in
Star Trek III. An actor other than Mark Lenard played young Sarek when Spock has a flashback to his birth in
Star Trek V. Star Trek XI is simply an extreme version of that same recasting. Certainly, the fact that Leonard Nimoy is in the film as old Spock implies that all of these guys will eventually grow up to become the actors that we know & love from The Original Series & the 1st 6 movies.
Superman Returns is somewhat more of a reboot but not really. The whole thing is a lengthy homage to the Richard Donner films but all of the roles are recast except for Marlon Brando as Jor-El (and I think maybe there's a photo of Glen Ford as Pa Kent somewhere in there). The timeline is somewhat different.
Superman: The Movie was clearly set in the 1970s but 2006 tech abounds in
Superman Returns. Lex Luthor is far more menacing in 2006 than he was in 1978.
Personally, I'm a big fan of
Superman Returns. I think it succeeded not because it was or wasn't a reboot but because Bryan Singer is just a flippin' brilliant director. However, I think it did help that it felt free to draw on the legacy & backstory of the Richard Donner films. (If only they had gone with more of a post-Crisis Lex Luthor, I think it would have been perfect.)
I'm a big fan of the current
Battlestar Galactica but I've never really seen the original, so I've got no basis for comparison. But if I were a fan of the original series, I think I would be up in arms over the reboot. For one thing, it stifles opportunities. Why rebuild when you can build upon what has come before that made it popular in the first place. After all, the idea to add on to the continuity instead of rebooting it was how we got
Star Trek: The Next Generation. The new
Doctor Who has also proved that you don't need to get rid of what has come before.
Batman is a slightly different animal. There have already been so many different iterations of Batman in the comics & TV shows. Even the continuity between the Burton & Schumacher movies was pretty loose. The only consistencies between all 4 films were Michael Gough as Alfred & Pat Hingle as Comissioner Gordon. Chris O'Donnell played Robin in both
Batman Forever and
Batman & Robin but there were 3 different Batmans-- Michael Keaton, Val Kilmer, & George Clooney. There were also 2 different Harvey Dents-- Billy Dee Williams & Tommy Lee Jones. Christopher Nolan's take on the character is yet another take on a character that has been interpreted a wide variety of ways. I loved the Tim Burton movies. I love
Batman Begins &
The Dark Knight too but in very different ways. I also loved the 1990s animated series. When I was a kid, I loved the 1960s Adam West TV show. And I suspect I'll love the next big screen incarnation of
Batman as well (unless it super sucks, like
Batman & Robin did

).
Even Judi Dench's M, the only element to remain constant, is played with a much harder edge, as if a different character.
I don't get where you're getting this. Certainly I think Dench's M was just as harsh in
Goldeneye as she was in
Casino Royale.
My feeling about
Casino Royale is that it could be a reboot but in some ways it's just a prequel to the 1st 20 films. It just so happens that, considering time never seems to actually pass in the James Bond series, every era that Bond is in is automatically the present, even if we are witnessing his past. Bond's existence is a non-linear existence. (The Cold War prologue of
Goldeneye is the one time this theory doesn't really fit.)