The number of existing games is huge and so is the number of games classification systems. You actually can classificate games any way you want, even according to how much money do you want to spend. Or games would rather be divided according to how much money do you want to earn. (Why not?). But there is a  a generally accepted classification of gambling games. You can check it bellow:

"Unbeatable" Casino Games (All players must lose in the long run no matter what strategy chosen): 

Slot machines  

Baccarat  

Craps  

Roulette  

Keno  

Casino war  

Faro (All but extinct in recent times)  

Pachinko  

Sic Bo  

Let It Ride  

The Wheel of Fortune  

3-card Poker  

4-card poker  

Red Dog  

Pyramid Poker  

Caribbean Stud Poker  

Spanish 21 -- without counting  

"Beatable" Casino Games 

With proper strategy, the smart player creates a positive mathematical expectation  

Poker (Also recognised as a game of skill)  

Blackjack -- with card counting  

Video poker -- with proper pay table  

Pai Gow Poker and Tiles -- player-dealt  

Sports betting  

Horse racing (pari-mutuel)  

Slot machines -- only linked, multi-player jackpots whose prizes have reached a certain point.  

Non-casino gambling games 

Lottery  

Mahjong  

Dice-based (Backgammon, Liar's dice, Passe-dix, Hazard)  

Card games (Liar's poker, Bridge, Basset, Lansquenet, Piquet, Put) 

Coin-tossing (Head and Tail, Two-up) 

Confidence tricks (Three card monte, The shell game, Carnival Games, The Razzle, Hanky Pank, Penny Falls, Six-Cat, The Swinger, The Push-up Bottle, The Nail Joint)  

Con Games (in bars) (Put and Take, The Smack, The Drunken Mitt).  

Another convenient way of game classification which is certainly will be useful for new comers are grouping games according to their popularity. We rated the large number of games and now can provide information for the most popular ones: card games, table games, slots, bingo games, keno, blackjack and baccarat games.