This scale seem reasonable?

10 "I can play this forever and not be bored, with my friends" (Starcraft: Brood War, Warcraft III, Battlefield 2, Smash Bros Melee, any Pokémon)

9 "I can play this game forever and not be bored" (Hearts of Iron II, LylatWars, Skyrim, Oblivion)

8 "Playing this game with my friends is great" (Guild Wars, Halo 3, Turok:Rage Wars, Smash Bros Brawl, Perfect Dark, Timesplitters, Counterstrike, Mario Kart 64, Mario Tennis 64, Streets of Rage 2, Golden Axe)

7 "Playing this game is great" (Super Mario 64, Zelda OoT, Banjo Kazooie, Sonic 3 & Knuckles, Castlevania The New Generation or Bloodlines, GTA: Vice City, After burner II, Any Total War, Peggle)

6: "Playing that game was great. Replay? nah..." (Eternal Darkness: Sanity's Requiem, Final Fantasy VI, Starfox Adventures, Bioshock)

5 "Was alright, might play it again" (Gauntlet: Dark Legacy, Defcon, Age of Empires III)

4 "Was alright, don't intend to replay" (Zelda: Twilight Pincess, Turok by touchstone, Perfect Dark Zero)

3 "Haven't finished it and have no motivation to" (Final Fantasy XIII, Braid, Mario Galaxy 2)

2 "Got bored, stopped playing immediately, don't intend to replay" (Heroes of Newerth)

1 "This game is an insult to gaming"/"Betrayal most foul"/"The existance of this game makes gaming as a whole worse" (Ultima IX, Metroid: Other M, Command & Conquer 4, any shovelware)

10:  A game that lives up to my every expectation--or better yet, surpasses them.  The total package.  Everything in life comes second to this game until it's completed.

9.  A game that is impressive in every way.  What many people would give a 10/10.  When I look at it, I can't really say anything bad about it but it's still missing something I just can't put my finger on.

8.  A very good game that is just shy of excellence.  Fun gameplay.  Maybe it has some technical issues.  Maybe it has some great ideas that weren't fully realized.  Still worth buying on day one.

7.  A good game.  Not really a "must play" but when you play it, you enjoy it and feel quite satisfied.  A sleeper hit.

6.  A good game with some issues that just can't be overlooked.  Poor button placement, awkward controls, long load times--on their own, they could be overlooked but this game is too unpolished in too many areas to be considered great.  Worth buying only if you're interested in the subject matter and it's the only option.

5.  A game that is just "there".  Doesn't do excel in any particular area.  Doesn't do enought things bad to make me hate it.  No emotional attachment to it whatsoever.  A time waster.

4.  A game that wouldn't even be purchased if it wasn't heavily discounted.  It may have one or two good things going for it.  A curious purchase or a rental.

3. A game that takes your expectations and ruins it.  May actually be better than a 5/10 or maybe even a 6/10 but it took something that should have been good/great and totally blew it.  This is more of an emotional score than anything.  Reserved for shitty sequels that fall way short of what their predeccessor offers.

2.  At least it works.  Not even worth opening if it's given as a gift.  (DS shovelware like Flight Attendent, Kawasaki Jet Ski for the Wii).

1.  A game that makes you regret playing it the second you start.  Absolutely no redeeming value whatsoever.  Poor graphics, poor controls.  An embarrassment of a video game.  You actually feel angry playing it.  Not even a "so bad it's funny" type of game.  (Wii Shovelware/Xbox Live Indie game cash grabs).

I think it was somewhere between 4 and 8, but it was forever ago so I'm not entirely sure.

10: Gaming Nirvana: Revolutionary, brilliantly unique and a near perfect gaming experience: Deus Ex & Half-Life 2

9: Excellent: Just a minor niggle or two that prevents perfection: Deus Ex: Human Revolution, Portal, Mass Effect 2, Skyrim, Super Mario World, Dragon Age Origins, Starcraft 2, FFVI & VII

8: Great: Well rounded experience but I'm not a huge fan of the genre or missing some features: God of War III, Age of Empires II, Tomb Raider, Prince of Persia, Crysis

7: Good: Either not a fan of the genre or I will play only when the mood takes me (so has some redeeming features) or both: Star Wars: The Force Unleashed, Resistance: FOM, Assassins Creed 1, Dragon Age II, Halo

6: OK: Dissappointing when compared to other games in the genre/series or failed potential: Call of Duty 3, GTAIV, Cursed Mountain, Bioshock 2

5: Playable.... just: I can play the game, but for the most part it sucks and I feel like it's a chore to play: Avatar: The Game, The Matrix game... actually, most film-to-game conversions

4: Poor: Developers have missed the point and even die-hard genre fans would struggle to find redeeming qualities: Final Fantasy XIII, X-2

3: Piss poor: Near impossible to find any redeeming qualities: Thrill-Kill

2: Unplayable: Literally, the game is unplayable. The mechanics are poor and it contains many horrific game bugs: Haven't played any but any Ubisoft PC game that uses their horrible DRM would probably count.

1: Developers need to be shot and their brains used as fertiliser as their lack of intelligence means they'd be of more use in the mud... lucky to say I have never played a game like this and I doubt I ever will!

I keep it simple
Anything less then 5 isn't worth playing
5 is barely worth playing
6 is almost decent
7 decent
8 good
9 very good
10 outstanding and almost perfect

10 Brilliant
9 Amazing
8 Great
7 Good
6-1 Crap

Scoobes 20 minutes ago

"10:Gaming Nirvana: Revolutionary, brilliantly unique and a near perfect gaming experience: Deus Ex & Half-Life 2"

lol Half life 2 revolutionary? no way man

I prefer a two-point system: Good and Not Good. Not that dissimilar to TruckOSaurus

Everything inbetween should be elucidated through writing/audio.