Looking at all the games systems that I've played on I'd say they're all pretty easy to get the hang of, although I didn't start gaming until the 90s and by this time the structure had been modified to make it more user friendly so you could enjoy the game without having to consciously think about which buttons you should press and so on.
There was a time around the mid 80s where games companies were experimenting with various external hardware ideas to regenerate an interest in the market again after the 1983 video game crash, creating additions to the consoles which were appealing because it presented gaming at a new angle. Yeah, it was a gamble with some of the new products they came out with and some of them weren't that successful but hey it's through trial and error that eventually they got it right.
If it ain't broke, don't fix it...
Nintendo has proved that the d-pad/AB button combination works wonderfully for so many games and the design is still popular with todays 7th generation consoles.
I think in terms of complexity the gameboy was probably the best way to introduce me into gaming, it is easier to get the hang of 2d games as the controls are a lot simpler... I mean I was only 10 when I first went on it but even my 3 year old cousin can play on my gameboy no problem o_O
It is amazing to think of how far gaming has come since it's early days, it has definitely progressed gameplay by providing the means for improved graphics and methods of controlling the game. The introduction of new innovative technology such as the wii and ds has extended the gaming audience dramatically as it presents the consoles as something that is accessible.
As new technology developed people suddenly became more aware of games. As with advancing computers, the design of consoles were pushed to fit the latest technology such as increased memory, better performance and graphics, whilst streamlining them to appear less bulky- making their exteriors more attractive in the home.
With the latest generation of consoles being so technologically advanced it's hard to say what the future of games will look like but I look really do look forward to seeing what they come up with next!
See ya ~Emi ^o^