Hard question to answer really.... it depends on the person playing the said games.  But my friend reckons that Ninja Gaiden black is the hardest.  I never played ninja gaiden so I can't comment on this but I have been playing games a long time (way back into the 1980s in fact) and I think the old school games are some of the hardest of all time.

I reckon that 'Robocop' in the Arcades was one of the hardest games ever, has anyone ever finished the game with only one life?  I can't even get off level 2 without continuing, and even now using MAME32 its bloody hard.

Then theres Green beret (Arcade again), you run from left to right with only your knife to protect you killing 100's of russian soldiers along the way.  I only ever managed to get to level 3 even on the spectrum I could never pass level 3.

What are other peoples views on what is the hardest game of all time to best......  plus I been searching the web and found this...

http://uk.pc.ign.com/articles/774/774907p1.html   top 10 hard games ever.

My friend walked up to me and said Street Fighter IV was the hardest game he has ever played, and plays it on Easiest, compared to me, who plays on hard. Snort.

The hardest game I ever played was F Zero GX story mode.

From what I've seen, Dragon's Lair on the NES.

AVGN did a review on the game as well.

In fact, when a speedrun for the game went up on Speed Demos Archive, people there were impressed that anyone could beat the game at all.

Truly hardcore.

lmao at dragons lair.

I had Green Beret on c64, loved the music if i remember... think i did alright, near past 1st screen or someting ;)

Super Mario Bros 3. Is damn hard, I've gotten to world eight, lost 40 lives, and now I'm too scared to try to beat it with 1.

i was right, green beret did have great music http://www.youtube.com/watch?v=0LorQ_zyBto

Super mario bros 3 hard? lol it was easy :P

If u told kids today games use to be on cassettes their heads would impode

No, your just not good at Mario games. It even took you forever to beat Luigi's Purple Coins.

 don't mention its name,  or it will visit you at night and make your skull melt

 I second that. Racing against the developers on the hardest mode... ouch.