As a collector of Yugioh cards, I have overpaid and been disappointed when I won an auction that includes the Yugioh God Cards and the seller claims all their cards are 100% authentic.  I am writing this guide to help fellow collectors and players who don't know how to tell a fake one from the real one.

Back of the God Cards:  The color on the back of the cards should match the color on the front.  Slifer should have a red tinted back.  Obelisk will have blue.  Ra will have yellow.  There WILL BE NO "Konami" on the top left of the card or the "Yu-Gi-Oh!"/Trading Card Games on the bottom right corner.

Front of the God Cards:  Like all authentic Yu-Gi-Oh! cards, there should be a square foil on the bottom right of the card.  If you tilt it against the light, it will show you the millennium eye and part of the words yu-gi-oh!.  Next to the square foil will be the copyright symbol and "1996 KAZUKI TAKAHASHI".  Check the spelling, some god cards has spelling mistakes in the copyright line. 

On the bottom left corner, there should a japanese characters for the card series G4 and GBI series (see next section).  If you have one of the other promos (YMA, DOD, JUMP), the card on the bottom left corner will say "This card cannot be used in a Duel." 

If you have a card that says "1st edition", it's a fake period.  If your entire front of the card is glossy, it is a fake.  All god cards will follow all your other rare cards.  That means the picture and the text are the only shinny parts on the card.  In addition, the fake glossy card will seem to weigh heavier and feel more rigid.  Of course this is tough if you don't have a original one to compare to.  The are some glossy cards in the Yugioh series and they are the parallel series of card.  Don't let a seller tell you that these god cares are parallel series.  As of this date 04/2008, there are NO god cards in parallel print which means that no god cards will have the entire front of the card to be glossy and be rigid.

Another give away is the font that is used on the fake cards.  The word "DIVINE-BEAST" and the "ATK/..." don't match.  Meaning the fonts seem bigger and thicker in "Divine-Beasat" and the "ATK/..." seems skinner.

Check your dragon of Ra, if the card has "ATK/ ????  DEF/ ????", it is a fake.  What you might ask is fake with that?  If there is a space between "/" and the "?", it is a fake.  The real dragon of RA, there is no space.

If it is an ultra rare card, the name should match correspondingly to the picture (see rarity guide below).  I came across of ones where the name of the card is silver but the foil picture was like an ultra foil or vice versa.  Gold text and the foil picture was like a secret rare foil.

Card Series:  (see rarity guide below for explanation of ultra, secret rare)

Slifer the Sky Dragon

G4-01 (Japanese version - all writings in Japanese), this card was packaged with the Gameboy Duel Monsters Promo Series 4, this card is Ultra Rare.
GBI-001 - This card was packaged with the Gameboy Worldwide Editions Promo.  This card can be Secret Rare or Ultra Rare
YMA-EN001 - This card was part of the Yugioh The Movie Ani-Manga Promo.  This card is Secret Rare.

Obelisk the Tormentor 

G4-02 (Japanese version - all writings in Japanese), this card was packaged with the Gameboy Duel Monsters Promo Series 4, this card is Ultra Rare.
GBI-002 - This card was packaged with the Gameboy Worldwide Editions Promo.  This card can be Secret Rare or Ultra Rare
JUMP-EN004 - This card is a SHONEN Jump magazine promo card.  This card is Secret Rare

The Winged Dragon of Ra

G4-03 (Japanese version - all writings in Japanese), this card was packaged with the Gameboy Duel Monsters Promo Series 4, this card is Ultra Rare.
GBI-003 - This card was packaged with the Gameboy Worldwide Editions Promo.  This card can be Secret Rare or Ultra Rare
DOD-001 - This card is came from the XBOX Dawn of the Destiny Game promo card.  This card is Secret Rare.

There is another set WC08 series for the Yu-Gi-Oh! World Championship 2008.  I haven't seen any of those cards in the items I have purchased or the many auction items in ebay.

Here's some links that has a picture of the real god cards (make sure you put http://, ebay guide will let me link directly)

I hope this helps you a little in determining if your cards are real or not.  If you are thinking of buying one from an ebay auction, ask the seller to take a close up picture of the card.  If you still can't tell, take it to your local collectible card shop and they'll be able to assist you.

Good luck and if you are a card player, remember to play hard but play fair!

Rarity Guide: