you make some good points, so let me try and reply to some of what you say...
first, Mike & Dave shouldn't have been in my post. I though they were under $20M budget and see now that was wrong.
however, I respectfully disagree on Jungle Book. the audience and critics loved that film. if they keep the budget in line, there's wide appeal. the reason I trashed Alice so early on is for all the reasons you mentioned. the closer it got to release the more I felt it would do REALLY bad... but for as horrible as it did, nobody thought it would perform THAT bad. and with the success of the first, it's safe to say NOBODY questioned the talk of a sequel at the time. it was a perfect storm of bad timing and saturation of similar films in the industry... and a mediocre 1st and 2nd outing.
NYSM2's WW numbers are so great though, you just can't ignore the profit potential which is why this is primed for a 3rd.
Barbershop 3 had a $20M budget and I read a while back that the film was a success (even though each sequel has decliend $10M off the last film).
so how many is too many sequels?
answer this question. is there a film on this list you feel should not get made, from strictly a profitablity perspective...
Pets 2
Zootopia 2
Central Intelligence 2
Bad Moms 2
Lights Out 2
The Shallows 2
Sausage Party 2
Angry Birds 2
Jungle Book 2
Deadpool 2
Suicide Squad 2
Batman 1000
Superman 3
Dory 3
Captain America 4
Conjuring 3
Cloverfield 3
Ride Along 3
Purge 4
that's 19 films that have came out in the last six months alone. let's say they all went into development now to be released in the next 2-3 years, you can quickly see how in a given year you might have 30-50 wide release films just from the same well. this on top of the countless other properties.
while properties like Pirates need to die, it's up to the studio to make that call. by the way, Pirates is going to perish next year domestically. the budget has soared past $320M, so it's going to be tough to even get square from a WW perspective. Disney has to be worried about that one. I can't take credit for solely mentioning this, as I've spoken to some people that allude to these worries from first hand sources.
I think the problem is knowing when to quit. many of the comments in this thread hit on that and peopel are making great points, but the more these original films take off, the more they are primed to be re-developed into a sequel. in most cases, people want to see a sequel relatively soon. nostalgia sequels can work, but timing and many other factors are imperative.
Dory lucked out because the children who grew up loving it, held it so high through their childhood and the teens that loved it, showed their now children. Ellen also has became such a huge personality in our social media age. the signs were there for this to be massive as a result.
where Fox royally screwed up is by not getting back Will Smith. that and they made a carbon copy (that was marketed like a parody) of the first film, with less starpower. in no way though do I think ID42 shouldn't have been made though, it just shouldn't have been made the way it was and without Smith.... and probably should have been released in 2000 for optimal returns.
if you really want to get sick, go look at 2017's release schedule. there is very little room for original films and that becomes less and less as the original films that succeed are turned into sequels and threequels and such.
I think it would be interesting to see what you would cut from 2017, to make room for an original property. then see how that film does from a profitability standpoint. say shed 12 films next year from the schedule and we can revisit and see how that goes.
maybe I'll try to work that into some sort of cool contest with prizes.