Since it was asked (about 15 seconds ago, by the looks of things). Here's my scale for 1-10 video game difficulty. Keep in mind, I never meant for this to be a cut and dried scale. Also, I'm generally talking about the main game, not those insane sidequests. Kingdom Hearts rates about a 5, beating Sephiroth in the arena would rank much higher.
1 - Nonexistant challenge. The game practically beats itself. Generally games this easy simply aren't enjoyable, as there's no challenge whatsoever.
examples: The first few levels of Tetris (you know... the really slow ones that you always skip because you're sitting there the entire time wishing the damn game would hurry up, already). Most games made for children under the age of 5.
2 - Pitifully easy. The game technically doesn't just lie down and ask you to beat it, but it still doesn't go very far beyond "interactive movie".
examples: Most 'casual' games (Plants vs. Zombies springs to mind),
3 - Pretty damned easy. You will be able to play straight through, only replaying the occasional challenge.
examples: Tony Hawk games, Most FPS' on lower difficulties, Super Mario Brothers II (with the obvious exception of Triclyde).
4 - Chill. Most games eventually find there way to somewhere between here and 6 with enough practice (even Megaman gets to be easy once you've got in completely memorized..........or so I hear).
examples: Most JRPGs spring to mind. I'm not talking about those crazy side missions where you have to kill a 900,000,000 HP monster in forty-five seconds using only a toothpick. I'm talking about the standard quests, normal grinding... that sort of thing.
5 - Perfectly average. The game neither falls at your feet begging for mercy nor beats you mercilessly over the head until you melt the cartridge down and mold it into an obelisk of torment.
examples: lots and lots and lots, but Knights of the Old Republic comes to mind right now for some reason. That game always seemed like a pretty good balance between "ah, i'm kicking ass" and "ah, I died".
6 -Slightly Harder. You'll die. Sometimes you'll die a lot, but there will never be that point where you simply get stuck.
examples: Diablo II, Bioshock, Vectorman, Scott Pilgirm: The Game
7 - Challenging. There will be segments of this game that you will get stuck on for a while. Never so challenging that it becomes a drudge. Probably my favorite difficulty level.
examples: Devil May Cry, Most SNES-style platformers (Donkey Kong Country, etc), Frequency
8 - Old school NES-style punishing. Throwbacks to back in the day when a game made you earn the crappy little "you win" ending cutscene.
examples: Most Contra games, Splosion Man, VVVVVV, Gauntlet (single player)
9 - Brutal Difficulty. There are points where I'm unsure I can beat the game, but with enough time and effort, it eventually becomes doable.
examples: most FPS' on their highest difficulty (I don't like playing FPS' on their highest difficulty), most of the earlier Megaman games
10 - Unfair difficulty. I'm reasonably convinced that I can't beat these games without cheating.
examples: NES Ninja Gaiden Games, Ikaruga, Battletoads (btw, fuck Battletoads), I Wanna Be the Guy