I have played the downloadable Mario Forever game. But both the flash version and the other one suck, and disappoint me.
But I'll just talk about this one. My very major complaint is the fucked up controls. Who the hell uses Z to jump?! Usually it's the other way around, you know, the button before jump is run. Speaking of running, there is not absolute way to move any slower, or faster. Seriously, it takes time to get used to the crappy controls.
The jumping works okay, but the gravity is too fast. You go into the air too fast, and fall too fast. When I played the first official Mario game, that never did that to me.
Graphics are really nothing much to complain about. It's clear that it was ripped from the SNES version of Super Mario Bros. 1, but there are still things that get on my nerves.
Take the bricks for example. If you destroy them with your head, they don't shatter into pieces, oh no. Instead, it just gravitates towards the air and falls off the screen. What happened? Did the brick slip off the cement?
Also, there's some serious problem with the fire flower. Whenever you throw a fireball at an enemy half of Super Mario's height (when he has the mushroom), it often bounces off the ground and deliberately AVOID the enemy. That's some serious handicap.
The physics are almost as if this game should've been put in the context of SMB3 or Super Mario World. It's pretty slippery and you start running too fast. I would REALLY apprecciate it if running could be done with the Z button, but no, there is no way to move any slower.
And let's talk about the Bowser boss fight. Who would think to stomp on him? In the first Mario game, you have to either get the axe behind him, or pelt him with fireballs for fun. But stomping on him can go against any instincts of a Mario fan. And stomping on Bowser is no easy thing. If he ever jumps, or becomes invincible for a second, you are prohibited from attacking him. Otherwise, YOU get hurt or killed.
When I played the downloadable version, it really frustrated my younger childhood, and still pisses me off today. Why? Because the 7th world is impossible.
I'm trying my least to be a jerk, but I'm baffled how most people are missing out the real bad aspects of this game. I just can't lie. This game (probably) sucked back then, and sucks forever.