Dedicated video game stores : they can vary a lot between locations, and are often dependent upon the employees that work at them. For example we have a great ebgames where I live with GREAT employees who will bend over backwards for their customers, however others will report radically different experiences, most will report bad experiences, as an EbStop store with good employees seems to be a rarity nowadays. Biggest complaint about Ebstop is that they sell used games as new and the "open box" copies of games, try to avoid this as possible, as its pissing off a lot of customers (including myself). If a game is new, it should be sold as a factory-sealed (non store re-shrinkwrapped) shrinkwrapped copy no exceptions. Ebstop is also notorious for raising the prices of games by 5$ per title over MSRP, especially on Nintendo DS games. We do not like to pay 34.99 for a DS game that has been opened, for whatever reason, when the store next door has factory sealed copies that we know have never been played. There has even been a lawsuit for EbStop selling used products as new, and to my knowledge they still do it. Another thing they do wrong is condition of used merchandise, everything is scratched to the pits, and the merchandise quality seems to be decreasing daily in those stores. I could go on and on about what gamestop does wrong, but most of it has already been covered in this thread. What they do right... hmm there isn't too much, maybe carry games that other retail stores do not, but with the internet, if we want obscure games, most just order online these days, its just easier and more convenient, plus Ebstops selection of games seems to be decreasing every day and getting just as bad as normal retail stores, at least where I live. Oh they give out bonus items that other stores don't, thats a major plus. Employees here are just as pushy to sell extra's and warranties if not worse than big box retail stores.
Big box stores: Impersonal service, often games are locked up behind a glass case and its difficult to find an employee around to open it up and get the games out (this varies by store though, at sears there is always an employee around, but at kmart hunting down an employee might take you about 20 min). Then the employee doesn't even know which key opens the case and sometimes the locks break and then don't open for weeks... so the games are literately locked up and you cannot get to them at all no matter what you do. They always have factory sealed brand new copies of games that you know have never been played though. Toys R us has the best business model where they put games in plastic cases to prevent theft but allows you to look at the box while purchasing, and you can just go and pick your game then head to the register with out any hassle, circuit city also does this and its the best way to go, I like it the best. Usually employees are not knowledgeable about games, but this can vary by store. Sometimes retail stores inflate the prices of games too, but that rarely happens with the exception of EbStop. The best thing retail stores do is clearance games when they aren't selling, which leaves many cheap games for us to snag! Retail big box stores can be very pushy when it comes to purchasing warranties and extras with an item so if you don't want to be sold a 100$ set of A/V cables with your game system, or a 30$ one year warranty when your Nintendo system already comes with a year warranty from Nintendo, you might want to head to an online store to avoid the hassle. Long lines at the register, not enough cashiers, could take a long time to get out of the store due to register employees being forced to push 30 different extras on you for a single purchase of a video game, and if there are long lines this makes the experience even worse.
Just remember with big box stores and dedicated game stores they often hire people that just know how to sell items, and may not know anything about the product in question other than what accessories and extras to sell you with the item. Retail is becoming more and more like the job of a used car salesman or a car salesman nowadays, the more stuff they push on you, and the more you buy, the better for them, regardless if its an item you need or not, a useless warranty, or a magazine subscription. They just want to sell you as much stuff as possible since it makes more profit for the company.
Online stores - what they do right, pretty much everything. Online stores have the lowest prices out of everyone, and you can often save money off the retail price by shopping online, which is why I shop online a lot. Also no tax usually which is a major plus since I live in NY state and I am docked 8.75% every time I make a purchase, and with large video game purchases that can add up fast. Shopping experience is quick and easy but returns should you need to make one could be a hassle depending on where you order. Fortunately Amazon makes the return process really easy. Biggest selection of products available anywhere, most of the time I look online to find things that the retail stores in my area just do not offer, as retail big box stores only offer a very limited selection of games, which does not usually cater to the tastes of an adult gamer (they usually stock 30 copies of kid game x but fail to stock an Atlus title for example). I am a big advocate of online shopping (especially for small electronic items such as video games) as it saves the consumer a lot of money in the end. I would also say impersonal service too as your not dealing with any humans, a lot of online companies hide their phone number and contact information too so they can be hard to get ahold of should you have a problem with your order. Fortunately information about online stores is usually readily available so you can make a decision about which stores to use and which to avoid. Lack of product information at most online stores as well, this isn't a problem if you know what your buying but for people who have never bought a video game before they may prefer a B&M store with employees.