Destroy All Monsters seems like the kind of movie people seem to tell you is one of the best, but never explain why.
The plot is pretty much a more widescale version of Monster Zero with Aliens taking over all the monsters rather than just two. The monster island idea is great, but outside the opening not much is done with it. Would have been nice to see it more fleshed out. The characters are ok at best, they just go through the motions it seems, never really grabbing me outside of some scenes.
Even the final fight, although entertaining wasn't that great. Despite the huge roster the fight essentially became another 3v1 vs Ghidorah, something we've seen before, with Anguirus replacing Rodan and Gorosaurus replacing Mothra. The other monsters do a little but nothing noteworthy during the fight. I know the wirework restricted a lot of the monsters from participating but still, urks me just a little that after being in every fight with Ghidorah prior and having basically the same rivalry with him Godzilla did at this point Rodan didn't do anything in the final fight. The fight the kills Ghidorah and Rodan doesn't do anything instead Gorosaurus is in the fight...
Anyway it has its moments and some iconic scenes but outside that I don't find it to be as strong as a lot of people seem to insist it is.