When people use the term "best" they usually refer to "favorite." At least in terms of media such as books, movies, video games, etc. However, the game I consider to be the best designed of all time happens to not be my favorite game (that would be secret of mana for the snes). Because to take into consideration truly monumental design, you have to think beyond your personal tastes.
How many games in the history of gaming truly appeal to everyone? Whenever there is a topic of best game of all time, it's not uncommon to see the likes of metal gear solid (ps1), Legend of Zelda: OOT (n64), Final Fantasy 7 (ps1), etc. While these are great games and favorites of many everyday gamers, they are unlikely to be equally enjoyed by said gamers little sister or parent. Fact of the matter is, they aren't easy titles for just anyone to get into. They take time to get into and a certain kind of mindset to master the control mechanics.
The farther gaming moves forward, the more simple game mechanics have become shunned. The term "casual" has become an ugly term used to somehow devalue games that are meant for a wider audience. However, many of these same gamers grew up with beat-em-ups and 2D side scrollers that relied on 2 buttons. Sure some games required a certain amount of mastery, but what about such classics as Streets of Rage 2, TMNT: Turtles in Time, and kirby's adventure? All are great games but pretty much as "casual" as you get.
All this leads me to what is (in my opinion) the greatest crossover title of all time: Mario Bros. 3.
I know it's not really an original pick but I've perhaps chosen it for less common reasons. Of course, there are the obvious high points: The graphics (which have held up), the sound (still great), the amount of overall content (still considered good bang for your buck, even by today’s standards). But there are other things which aren't often brought up. The early use of an in game save feature and level select. The two player competitive play, both alternating and simultaneous.
Then there are the play mechanics. Mario Bros. 3 is truly one of the few games that just about anyone and play and just about everyone will love. The stages are all reasonably short to encourage replayability and the difficulty is balanced in such a way that even brand new gamers should be able to have a fair amount of success throughout the first few worlds.
So, for "Hardcore gamers:" You have a title that pushed a systems tech for all it was worth, and created a lengthy experience that was easy to get into but a challenge to finish. And for "causal gamers:" You have a lively and inviting presentation, simple play mechanics, fairly short stages, and a novice friendly difficulty curve.
So yeah, all opinions are welcome and I'm sure I didn't write the most fluid piece, but that's my reasoning for Mario Bros. 3 being the best-designed game of all time.
