For me, a couple are Dragon Warrior 2 and Mega Man X2(which was the last I played of the Mega Man X series).

The hardest game I have ever played is still Super Ghouls 'n Ghosts for the Super Nintendo.

It took me 10 years to get to the third level, mostly thanks to this to part here:

http://img.gamespot.com/gamespot/images/2007/093/reviews/938369_20070404_screen003.jpg

The hardest game I ever played was "The Super Spy" for the Neo Geo

http://www.videogamecritic.net/images/neogeo/super_spy,_the.gif

Since it was also an arcade game, if you had enough quarters, you could beat it, but the game itself had a few bugs.  Sometimes when you tried to go down a hallway, it wouldn't quite let you, so more enemies would appear, and in order to proceed, you'd have to kill them off.  On the 3rd floor, you get a pair of brass knuckles on the hand that you don't punch with.  After you used your knife so many times (12 I think it was), the blade would go dull and it wouldn't really do any damage to the enemies

When the MAME came out, I downloaded Super Spy, and the amount of credits I used to finish the game would have equalled over $70.00 in Quarters (I did the math to get the actual number, but I don't remember what it was)

The EASIEST game I ever played.  Not including cheat codes and Atari 2600/7800 games, I'd say it is the Turbo Grafx-16 version of "Vigilante"

http://www.videogamecritic.net/images/t16/vigilante.gif

I don't want to say it was too easy, but when I got it for my birthday, I finished it very quickly on my first try.  The trick with the first few bosses was that you could stand in one spot, and essentially keep hitting them and they would be in a frozen state.  If you had the nunchucks, it worked even better

^ I've heard of Vigilante, but never played it.

I forgot to mention that Dragon Warrior 2 and Mega Man X 2 were two of the hardest games I played.

For Dragon Warrior 2, the things that make it hard are some of the unfair enemies that you run into. There are some that can drain double digit magic points with the strange jig plus others that have group target based breath attacks and attack spells. Even when you max out your party's experience levels you can still be wiped out, because there are enemies in the final area(Rhone) that know the instant death spells Defeat(which doesn't always work) and Sacrifice(which I've yet to see fail when they use it on me). This is one of those games which you have to level abit more often to keep from getting murdered easily.(I've seen people on message boards not level too much and get annihilated in the cave that goes to Rhone) This is one of those RPGs that has several areas where certain enemy groups give you that feeling of doom looking over your shoulder. I know I listed at least one or two enemies from this game on my "enemies you fear" thread.

Mega Man X2 is just more challenging on whole, I've heard the later ones are just as well.

As for easy games, one of the easiest games I ever played was The Little Mermaid on the NES(I rented it before), beat it that first night I had it.

SimCity Societies is embarrassingly easy. I lost interest in it after a couple of hours.

Easiest? I dunno, there's been quite a few of them.

Hardest:

Urban Slug, here in the arcade: this game is so buggy (imo) and difficult that I've only managed two or three scores over 100 in thousands of plays. I have no idea if there's even an "ending".

Everquest: This game goes from interesting and cool to massive time and money sink as well as impossible if you don't play it 40 hours a week with 5-30 other people who spend the same amount of time doing so.

Gauntlet (arcade): Ditto Urban Slug, except that quarters run out faster than patience does. I've never played another arcade game that required 1/10th the money that one ate up.

Ant

easy  I played and got bored of some Sonic games pretty quickly.  Eggmans inventions were too easy to beat. Unless you're under water all you have to do is make sure you have a ring.  The Mad Monket Banana Toss thats here is  The game that doesn't end


hard Comic Zone  maybe I just can't control the guy well.  There's a boss with long fingernails I haven't passed yet.  I think he's on level 3
   

easy  I played and got bored of some Sonic games pretty quickly.  Eggmans inventions were too easy to beat. Unless you're under water all you have to do is make sure you have a ring. 



I agree about the Sonic games. I have not played any of the newer games in the Sonic series since it transferred to 3D, but the original 2D games are all pretty easy. The easiest is probably Sonic 3, which only has 6 levels and gives you the ability to save your progress. On a good day I can beat that game in between 30 and 45 minutes.

i've been messing around a lot with EA madden lately and i'd have to say it's a lot like an old quote i heard about guitar, which is that guitar is one of the easiest instruments to learn but one of the hardest to master. and i think this game is much the same.