As stated, you can
get better deals locally and off Craigslist.
It really depends on your area though, around here the local game shops charge an arm and a leg for anything good. For example, one of them was selling Chrono Trigger for $110 when you could get it for $85 on Amazon or Ebay. That was a couple of years back. The same shop wants like $30 for a copy of Super Mario 3 for NES (should be $20... but if I were selling it out of my garage I'd probably ask $15).
There is one good game shop here but it's smaller, not a chain, and the selection is usually worse. He has a ton of Game Boy games for example, but they're all junk...stuff like Barbie, Avatar the Airbender, Wizard of Oz and other games no one ever wants. Occasionally I get cool stuff from him at a decent price. A few years back I got FFII for $30 and FFIII for $40 (SNES), those were great prices at the time, and they're worth a little more than that now.
Tbh I'm at the point in my collecting where pretty much anything I want, I am going to have to get online. One of the few Genesis games I wanted but didn't have was Gunstar Heroes. In close to 7 years of checking the shops here I haven't seen it a single time. And I bet if I had, that one shop would want $100 for it. Well, I paid around $60 for it on Amazon.
My suggestion would be to check all the used games stores in your area, and if you don't consider it rude... bring your smartphone and check Amazon and Ebay prices for games before you buy. If they're asking $10-20 more than the cheapest price on Amazon, then it's probably a bad shop. Even if they pay half the cheapest Amazon price for a game, they can still make money selling it for the Amazon price. I've even heard stuff like, "but it costs shipping to get a game from Amazon, so if you buy it from me you won't have to pay shipping and you can have it now"... sorry but that's no reason to add a $20 premium (or more). The really bad shops will just price a game way higher than it's worth due to it's notoriety (The Chrono Triggers, Secret of Manas, Megaman X2s etc)
has basically the most fair and accurate prices for games nowadays. The guy at the GOOD shop here in town (Lance) uses this site and Ebay to price his games and it's the reason his prices are fair. (For example, pricecharting says that a loose Mario 3 is worth $15. That's pretty much right. Lance sells it for $20.)
If you're buying from Craigslist, look for bundle deals. I had good luck with Craigslist twice but one time I had to drive rather far to get the games. Once I got like 10 Game Gear games including Shining Force: Sword of Hajya ($30 by itself) for... around $30. I got a Streets of Rage and two Shinobi games with it too. Another time, some guy out in the boondocks was selling NES games, and I paid like $65 for Mega Man 6, TMNT 2, TMNT 3, Zelda Link to the Past, Adventure Island and like 10 other NES games. Just Mega Man 6 at the time was worth $50 and Link to the Past for SNES was worth $30. So try and find those guys that resell old games as a hobby and will give you a bundle deal. Often times, you can talk them down and get a bunch of games for way less than they'd be individually on Amazon.
Another one that wasn't mentioned: ask your friends if they have anything they want to sell if they're gamers. They might have old consoles in an attic, a storage locker, the basement etc. I got Shining Force II for Genesis for $5 from a friend this way ($40 game now). He also sold me SFII:CE and two 6-button Sega brand Genesis pads, and like two other Genesis games for $20. I got my Saturn from him with two controllers, a game and all hookups for $60.
Anyway sorry this was a long read but those are my tricks... hope this helps. Also, if you find something you want to buy but aren't sure if it's a ripoff or not you can always ask here.Edited by neurotix - 6/14/16 at 11:36am