I must first say I did not beat this game without using the konami code as a kid, but having not played the game in ages I picked it up and played it.  I beat the game only having to use 1 continue on the second base level.  I remember seeing this as the hardest game of all time in some places, and perhaps it was harder back then when people didn't have years to sharpen their skills in similar games i'm not sure. 

Contra 4 is far more difficult, normal difficulty on Contra 4 is probably harder then Contra.  Hard mode is way harder.

Contra depends a lot on the player skills, reflexes and ability to manage a lot of oncoming bullets. That being said, it's difficulty relies on those factors, so while some people will find the game extremely hard, other people with more pratice will find it not so hard.

In my opinion, Contra wasn't as hard as Ghouls 'n Goblins, Battletoads or Demon's Crest

oh god ghouls and goblins is tough. I got all 3 of them on virtual console and I beat the SNES one a few times, but the last level on the NES one is ridiculous. I kinda gave up on the genesis one.
Took me a long time to beat castlevania 1, that was quite challenging as well.

The NES version almost made me throw the controller through the TV, especially since when you actually manage to defeat Beelzebulb, you'll only find out that you have to play the game again in even tougher levels to actually finish the game... xD

Castlevania 1 was hard as well, but I find Castlevania 2: Simon's Quest even harder, since the off-screen projectiles really give you a hard time

And that reminds me of the original Ninja Gaiden trilogy, gods that was hard as hell too xD

It is always fun to go back and play games from the past to see how much our skills have improved. :)

When you wrote that you beat while using only 1 continue, did you beat it without the konami code?

I beat all those games, except the toads...

Contra 4 kicks my ass, but Im sure with pratice I can beat it

I've only played the Ghouls 'n Goblins on the PSP but it was tough!
And Contra isn't crazy hard, once you get the controls down and get used to the dodging bullets and stuff it isn't that bad.

Battletoads is my true gaming hell xD I still have nightmares about the Tunnel race level...*Shivers*