A lot of auctions on ebay have the heading 'RARE'. As an absolute console junkie for the last 20 years or so I have had a lot of rare games pass through my hands (albeit mostly unknowingly). Typing 'rare' in to your ebay search bar will undoubtedly throw up a load of 'not rare' crap. Besides, just because a game is rare it doesn't mean that it will be any good, (take 90% of the Sega 32X tiny library for example) on the contrary most of the very best games are released in HUGE numbers, almost all of the Mario games were best sellers, and a lot of them 'pack in's' sold with the consoles themselves, yet people still seem to think that they can call games such as Super Smash Bros. Melee and Mario Kart Double Dash 'RARE' the latter incidentally was the highest selling Gamecube game of all time, at 6.6 million copies sold, it definately aint rare, just a very good game thats all. Sonic 3 and Sonic & Knuckles also pull quite a lot of money on ebay under the pretence that they are 'RARE', it's Sega's mascot ferchristsakes, it's what sold the Megadrive, they are going to make truck loads of them aren't they? The best way to find out if a certain game is rare or not is simple, all you have to do is type in to your favorite search engine ... '(insert console name here) games rarity list'. There are tons of rarity lists to choose from. When you have come across a genuine rare game on ebay, why not find a review of it on the net to help you decide before getting into a bidding war with hardcore games collectors, who are willing to pay high prices for old games. Dont forget these games are ALWAYS selling on ebay, if you loose a bidding war, so what .... just keep an eye out for the next one. If you paid £30 for Streets Of Rage 3, then good for you. Is it rare? Is it a 'must have'? Should you splash out on a 15 year old video game for silly money? ............ probably not. Do plenty of research and play test the game on an emulator if you can. You should be able to build a nice affordable game collection, tailored to your taste and pocket.
All stats taken from The Guiness Book Of World Records: Gamer Edition.