Here's my all-time list. Excluding prog and synthpop albums that I love personally, but which don't belong in a powerpop list, even using a wide criteria for what may be considered powerpop:

1. Skylarking - XTC
2. Pet Sounds - The Beach Boys
3. Woodface - Crowded House
4. Odessey & Oracle - The Zombies
5. Temple Of Low Men - Crowded House
6. High Land, Hard Rain - Aztec Camera
7. Sgt. Pepper's Lonely Heart's Club Band - The Beatles
8. No Sleep 'Til Famous - The Merrymakers
9. A Hard Day's Night - The Beatles
10.Free Peace Sweet - Dodgy
11.Together Alone - Crowded House
12.Nonsuch - XTC
13.The Original Soundtrack - 10cc
14.Homegrown - Dodgy
15.A Night At The Opera - Queen
16.Surf's Up - The Beach Boys
17.Bellybutton - Jellyfish
18.From Langley Park To Memphis - Prefab Sprout
19.Revolver - The Beatles
20.Radiator - Super Furry Animals