I find your lack of passion disturbing.
First Becky or second Becky?
First Vivian Banks or second Vivian Banks?
First James Rhodes or second?
First Bruce Banner or second?
First Rachel Dawes or second?
Choose wisely, your WTFIQ score depends on it.
I'm being glib of course, but recasting comes in two different flavors-- those recast early in the history of the character, and those that come later. Then there's whether or not there was a change to the character along with it.
The first Darren was pretty well established and the second changed the character significantly. The first Becky was around longer, but the second was a much better actress. Hard one to call. Marvel's recasts may have seem jarring at first, but now their second string has much more screen time than the first.
But none of these are truly iconic characters that are also played by one actor primarily. On the opposite end of the spectrum, James Bond or Batman are major icons, but their recasting is a given at this point.
The only time I think we've seen something like this before is when the new Star Trek films were made. Kirk had only ever been played by one man. No matter how good or bad of job Chris Pine would do, to most people he would never be Kirk.
I wonder if we'd have been flipping out had the internet existed when River Phoenix or Sean Patrick Flannerly were cast as Young Indiana Jones. To me, that's the difference-- they aren't replacing Harrison Ford as Han Solo, they are casting a younger version of himself. It's not like this is going to be a series, or that he's going to star in more films (OR WILL HE). For now it's a one-off story about Solo's past, so ultimately I don't think it's a big deal.
It comes down to the role being so iconic, that the basic idea of recasting, under any excuse, the question becomes should you even bother doing it. Obviously, for a lot of people, that alone was a reason to not make this movie.
You guys are going to lose your minds in Indy 5 when Harrison Indy finds the Fountain of Youth and regenerates into Chris Pratt to continue the series....