You should not buy these Pokemon games:

• Pokemon Naranja 
• Pokemon Chaos Black
• Pokemon Blue Diamond
• Pokemon Frigo Returns
• Pokemon Quartz
• Pokemon Perla

Notes:

• There is a real Pokemon Diamond coming out next year but it will be easily recognisable as a real Pokemon game.
• There is another real Pokemon game called Pokemon Pearl and the Spanish for Pearl is Perla. However, the cover should have a Pokemon that looks like this:

NOT like this:

Why not buy them? Because they're fake. Most people already do this anyway, but if you don't ALWAYS google Pokemon games you suspect to be fake.

Pokemon games do have telltale signs of if they're fake or not. They will always have an 'Official Nintendo Seal of Quality' sticker (it looks like a gold circle with spikes) but some fake games will have this too,  however it may be faded.

Some games practically scream fake, Pokemon Chaos Black has a picture of 'Chaos' from the 'Sonic the Hedgehog' series on it which is most likely where they got the name from. Frigo Returns also has the character from Pokemon XD: Gale of Darkness on its cover.

Also, it should have a Nintendo logo (it will be red inside a red sort of tube) and should say 'The Pokemon Company' and have a 'E' rating.

Do not trust image searching because some of these fake games have pictures that look very close to other Pokemon games. For instance, Pokemon Naranja, it has a Celebi on the front (a real pokemon) and an E rating (note most won't have a seal of quality or nintendo logo) and when you put it into images you get a lot of pokemon images. However, if you google it normally, you should get something saying 'Pokemon Naranja - Data Crystal' which tells you its a hack.

Another good thing to do is to go on to the Nintendo website:

www.nintendo.com

and in the top-right should be a search bar. Type in the name of the Pokemon game you're thinking of buying (just make sure you get the spelling right). If the game is real, when you scroll down it should come up with a list of a few Pokemon games with the one you typed in in the list. If it's not, there should be a little 'No Results Found' sign in grey near the bottom of the black box. 

Just learn to search for the signs and you'll be fine.