My scoring system would be something like rocketpig's but I would sum up several aspects of the experience so people could have an idea of what to expect of the game in a nutshell. No numbers, just symbols with some descriptions about aspects of the game you might be looking for like learning curve, if the game is great for completist, challenging (from teddy bear difficulty to masochistic), repetitiously engrossing, mindless fun, etc. those kinds of things that rather than a score are a sum-up of my review.

 Yeah, that sounds exactly like mine.

 The problem with this sort of review system is that it doesn't take into account value. You may say "don't buy" to a game that's too short, or too shallow, or too bereft of features for $50, but the game might be a good value once it drops to $20.

I make myself a 20 point scale (1-10 with .5 increments)

Examples:
10: Ocarina of Time, Final Fantasy VI
9.5: Half-Life 2/Orange Box, Super Smash Brothers Brawl, Grand Theft Auto 4, Super Mario Galaxy, 64, World, and 3, Resident Evil 4, Chrono Trigger
9: Civilization IV, Metroid Prime, Viewtiful Joe, Halo: Combat Evolved, Call of Duty 4, Advance Wars
8.5: Guitar Hero (series), Banjo-Kazooie, Super Mario Sunshine, Paper Mario, Half-Life
8: Halo 3, Resident Evil (GC), Devil May Cry (series except for 2), Mario Kart (series)
7.5: Super Mario: The Lost Levels, Pikmin
7: Mario Party (series), most sports games (like Madden)

I generally don't buy anything I would rate below an 8, and even at 8-8.5 I usually only buy the titles that have good multiplayer. Since I don't have that much money, I focus even more so on 9-10 games, and only get games below that as gifts.

Exactly. It also doesn't account for rentals, which means someone would miss out on pretty good games that are too bloody short with no replay value like Heavenly Sword.

If it's a game I like, even 1 hour long, Buy.

I have not rented games for over 7 years. I ALWAYS buy.

0: Something unbeliavably horrible. Almost impossible to even think what could deserve this. This kind of games shouldn't even be allowed to be made.

1: Almost everything's been messed up. Don't waste your money on this.

2: There might be something good in this but something has been done wrong pretty bad. Probably not worth getting.

3: This game actually isn't too bad. Nothing exceptional but might be worth trying. I wouldn't recommend spending too much money on this one either.

4: Pretty good actually. Good ideas done correctly with only minor problems. Nothing too original, though, but still worth trying. Paying full price doesn't hurt too much.

5: A masterpiece having only some very small flaws. Most probably has some original idea(s) as well. Definitely worth getting, probably even worth some extra.

Well, anywaay I meant a 1-5 scale where 0 exists as well but only for some horrible games (read the description). Other descriptions might not be so accurate but 1 is meant to be very bad, 3 average and 5 a masterpiece. No 0.25s and such included, only integers. Also, the rating differs for different groups, eg. friends of genre, casuals, average gamer. Easy to pick up your score.

0-100 or whatever it's trying to be really sucks. While 50 is meant to be average, the actual average is some 70-80. These days we're also having more and more nearly perfect games, which actually aren't even close to perfect. Also, being sequels of a great game forces the points up and so does hype, even more.

Thumbs up? Buy

Thumbs down? Don't

Pretty simple.

1.0 - 4.9 crappy game - don't buy
5.0 - 6.9 average game - rent it
7.0 - 8.9 good game
9.0 - 10 must have