I know some people may point it out, and yes this exists already. If you didn't know, here's a link to the site http://retroachievements.org/

So for retro games, its already satisfying to beat/complete them. (Unless of course, you're playing a bad game...) But if you're an "Achievement Hunter" or just want some extra challenges, achievements can help with that. ie: Fable 2, I had to play an evil character for the first time in my gaming career because I wanted to 100% that game, and I kinda enjoyed it because it was very different...though being a piece of crap wasn't so fun. So it just makes sense to sometimes want some achievements in retro games.

So the retro achievements seems appealing then, right? Well...my gripes are that most of the achievements are community made. Sooo you get achievements like Contra 3, beating the game without a game over, without upgrading your weapon, etc. Which sounds tough, but doable. Then beating a Castlevania game without dying on hard mode...nice to see the Megaman 9 type of achievements...

And then the obvious problem for a lot of people which I can agree with, you have to emulate. I don't want to get a discussion started about emulation, but a lot of people including me prefer the original experience. Its why when my NES stopped working, I had to buy a USB gamepad that looked just like the NES controller, and add CRT filters to everything when I emulated the games I couldn't play anymore.

So before I sum this up, here's a TLDR for you.
TLDR Achievements are cool for retro games, but with hard community-made achievements and an emulation requirement, some may be skeptical or against it.

What are your opinions? Have you already tried this? Would you rather stick to your own challenges? Thinking about replaying a lot of my completed games to try these. (Fourth playthrough of Mega Man X...)

I have used retroachievements with retroarch. For me it is just a fun gimmick not really the driving force to replay some games.

I'm bad at coming up with my own challenges, so I feel that may be why I like the idea. But I can't say I'm willing to beat Friday the 13th on NES again using the rock only.