I didn't know there was an alternate ending. I've searched for it, and did find one that was somewhat abbreviated, as well as a truly ridiculous mash-up that stole scenes from The Cable Guy.
Sadly, a number of films of that same ilk are underappreciated, but I agree - it's an extraordinary vehicle. I wonder - had the alternate ending been utilised, instead of that in the original film - if it might have had more critical acclaim? Yes - I realise that would have been pandering. Not Peter Weir's gig at all. Ah well, as Life has ever been - plus ça change, plus c'est la même chose.
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I don't think the problem was lack of critical acclaim - most critics loved the film - as it was with people who either refused to see it, because they dismissed Carrey as a one-dimensional buffoon, or people who loved him *because* they saw him in that light, and were disappointed when they didn't get another helping of Dumb and Dumber.