Here's a review from my 12 year old son, Ian:
Destroy All Planets was a fine movie, just fast forward through the talking. There aren’t any important plot details you need to know, just watch the fighting. There’s quite a bit of stock footage, but you should watch it. It’s stock footage of monster battles, so it’s worth watching. I watched all of it and I regretted it. The talking was a waste of time. Gamera fights an alien monster who resembles a squid. Viras is the name of the alien and his main attack is to form a sharp point with the three tentacles upon his head and jump forward, stabbing Gamera, thus making Gamera bleed a large amount of bluish-green blood.
This was not as good as Attack of the Monsters(Gamera vs Guiron), but was better than War of the Monsters (Gamera vs Barugon).