A very stylish game i found again, i used to play a lot of hours back in the early 00's in my GENESIS emulator. Brilliant style, nice and unique artwork, and SEGA Genesis exclusive.
Killer game! Totally unique style, and way ahead of its time. I also always wondered why it never got the deserved attention.
Seems like all of us retro-gamers have a different favorite in the Double Dragon saga
Double Dragon III was technically very good, but because of the one-life-game-over, it was a real downer for me, as I never had too much patience with this kind of game... I smashed countless of ps1 gamepads playing PES/Winning Eleven, and I was already in my early twenties, so you can pretty much see the pattern... But only obviously 'cause you could get cheap alternates of them as replacements. Otherwise, I could always get a grip of myself
Back to Double Dragon, I was probably fortunate enough to be able to get my hands on the Japanese version of Double Dragon II for the Famicon (which probably came out earlier than the American version). Some kid in school had the Japanese (again, Famicon) cartridge, and for whatever reason he lent it to me. But I had an American NES, so I needed that sketchy cartridge adaptor to make it work... and the kid who owned the game didn't have it, so I had to get one myself. Remember: I was 10 years old, this is precisely late '89, early 1990 in Brazil. No internet obviously, no guides, nothing. I somehow got a crummy pin-adaptor to make the game fit the console, but it wasn't working. It took me almost a week to make it work, and by then the kid who owned it was already asking for the cartridge back. So I only played it for the weekend, but damn, was it awesome...
Castlevania 2: Simon's Quest was a tough one, especially without strategy guides
I got Castlevania for Christmas in '89 (surely, the American NES version cartridge), and it simply gave me the nightmares! Not because of the game's theme (including the music!), obviously. But because I was so obsessed on progressing within' the game, only to get completely stuck on "both sides": Left side was the "mountain-wall" in which you needed to kneel with the red crystal equipped. Right side was the "lake" (aka: un-jumpable body of water) which you were required to kneel with the blue cristal. But again, no internet, no guides or anything of the sort made it impossible to progress. Not to mention the in-game hints were all useless due to poor translation ("lost in translation, literally) from the Japanese version, so... It's really curious that the lead game designer Hitoshi Akamatsu cited "Maze of Galious" as a major influence/inspiration for Castlevania II (source: wikipedia), since I've never even heard of this game, but played its prequel "Knightmare" on the MSX as a young kid!!!

(All Konami classics, BTW)
Lastly, another game that I found it pretty hard (and also made it even harder when it came out 'cause again: no internet, no guides, or anything) was "Shadow of the Beast", an AMIGA game that got ported to several other platforms. I got the Genesis/Mega Drive version, and it also gave me the "nightmares"! Again, through wikipedia sourcing I could find out that my frustration was justified:
"In a retrospective article for Digital Spy, Mark Langshaw remarked that Shadow of the Beast "will always be remembered as one of many jewels in the crown of Studio Liverpool." Langshaw however said that the Mega Drive version was considered inferior to other versions, and because of its poor conversion rate, the game ran faster than intended on the North American Genesis console and "went from unforgiving to near impossible." Travis Fahs of IGN considered the FM Towns port a superior version of the game."
This is easily explained in the very first second of the game after booting it up: the Genesis conversion was made by Electronic Arts.