SUPER MARIO LAND / Nintendo / Game Boy
Super Mario Land is one of those games you have to cut at least a little slack for due to historical context - not just the first Mario handheld game, but one of the first handheld games period. It's more primitive than even the original games for the NES, but if you can manage to not expect it to function like the "big brother" games do and get used to its own little hinks and flow, it's actually a pretty competent and fun little platformer and a very respectable first handheld effort.
When I say it's more primitive than any other Mario game, obviously the graphics jump out at you, but it's also about the gameplay. There's some serious hinkiness in sticking the landings of Mario's jumps (due to not being able to course-correct while floating quite as well), there are some odd clipping issues, the fireball bounces once then flies off the screen, and Koopas no longer leave behind shells that can be kicked - just to name the biggest issues that pop immediately to mind.
It feels enough like legit Mario to work, though. Again, you've got to check your console expectations at the door and take it for what it is. Part of the different feel is simply the new (and underpowered) hardware it was running on, but part is also that Gunpei Yokoi (Gameboy hardware and Metroid / Kid Icarus developer) was at the helm of this one rather than Shigeru Miyamoto. So it ends up feeling more like a Flash fan-made Mario game, but a pretty good one on the whole.
The Yokoi influence also makes it feel idiosyncratic and experimental. This was the only 2D Mario game to dabble with Gradius-like sh'mup levels - first a submarine level in the second world, and then the game actually concludes with Mario flying a plane and fighting two bosses back-to-back in it. The level aesthetics also have all sorts of kooky stuff you don't usually see in a Mario game - the whole thing is a mishmosh of ancient Egypt, Aztec influences, aliens and even a random Japanese bamboo forest thrown in as the penultimate level for some reason.
This whole mishmosh takes place in the never-again-used Sarasaland, making the whole thing feel a little like Fever Dream Mario. It introduces a bunch of new enemies that were likewise mostly never heard from again. The one lasting element from this weird little game is Daisy, the princess-in-peril du jour who would later be shoehorned into the series for the sports and kart games (and probably so Luigi would stop jackin' it by Mario's door when Peach was over).
With just four worlds (with three sub-levels each) and a relatively low overall level of difficulty, Super Mario Land is a snack of a platformer, but not a bad one. You'll get frustrated with the slippery gameplay at times, but you're also absolutely plied with coins and extra lives to make up for it. And it pumps out some surprisingly good chiptunes for such an early Gameboy title too, courtesy of Hip Tanaka (Metroid and Kid Icarus composer).