Opinions:
-- Shovel Knight: I played the original game but not any of the expansions. Excellent homage to Megaman, very well designed, even though I never really came back

-- Metroid 2 -- Specifically, the fanmade version of it that Nintendo tried to kill. Balls hard. Absolutely epic music. It's rare that a game is made with this much love.
-- The Power -- A masterclass in metroidvania world design. Can navigate the whole map with ease, without getting lost and without the need for a fast travel system.

If you ever make the time, I do recommend trying out Shovel Knight's DLC campaigns. Plague of Shadows plays differently though the levels are mostly the same. Spectre of Torment and King of Cards are an improvement over Plague of Shadows due to the levels being built around their character's unique abilities rather than the same journey with a different character and a new final boss.

Ah yes, AM2R. I've heard good things about it and it's a shame that Nintendo tried to kill them off so they could promote Metroid: Samus Returns. I hear that the same fate befell Pokemon Uranium but it's possible that both fangames may've been recovered.