ALEX KIDD IN MIRACLE WORLD / Sega / Master System
The Master System was the only major console I can remember with games built into the firmware, which was a pretty cool feature. If you got one of the early versions, you got Alex Kidd in Miracle World as your main game if you flipped the console on with no cartridge in.
The game is all kinds of creative, colorful and full of interesting ideas, but it's largely ruined by having to constantly battle sloppy play control and some weird design decisions. Alex makes floaty, imprecise jumps and his movement is slidey, which isn't good when everything kills you in one hit and there's little shitty surprise deathtraps scattered everywhere.
There's also some weirdo choices in design that make the game aggravating. Boss battles consist of a "rock paper scissors" match, which reduces them to frustrating randomness rather than skill. Also, the game has no passwords or saves - there's a hidden continue feature that the game doesn't tell you about, which involves pressing the II button eight times on the game over screen, and also costs you 400 bucks. Why is this so obscure and hidden? Lol mid-80s game design.
* Gameplay Video