Fourth. All gaming magazines of the time considered it a 16-bit system and thus automatically a generation ahead of the NES/Master System. That was pretty much what defined generations back then. By the way, "bit" marketing actually lasted all the way to the middle of the sixth generation. Some people even had to be called out of calling the prospective PS3 etc. 256-bit consoles, back in the days of next-gen speculation.

Fourth Generation and it wasn't even the first one since the PC Engine/Turbo Grafx-16 was released almost a year before it.

https://en.wikipedia.org/wiki/Fourth_generation_of_video_game_consoles

You can make an argument that the PC Engine wasn't a true fourth generation system since it had a 8 bit CPU and it had a two button controller.

It is obviously same gen as SNES, they were direct competitors sharing similar games for most of the time.

And I first heard about gen probably when PS1 launched as next-gen and then saw the 8-bit, 16-bit, etc.

Videogames are not tech generation, it's all about time. The prime sega genesis years clash to SNES best years.

Videogames are not a tech focus, but entertainment focus. What sells are games, not the tech. 

Those were the days.

Can't really use "bits" to define a generation.

The Nintendo 64 had a 64bit processor and was a 5th generation console.
The Original Xbox had a 32bit processor and was a 6th generation console.

No, Genesis/Mega Drive wasn't essentially re-entered 3rd generation, you gotta know that SEGA used to make hardware ahead of time.

*Yes*. The first commercial tells you Genesis is a brand new next gen console came with 16 bit CPU & the rest awesome chips that does handle higher resolution, more colors and more smoother animation while the NES doesn't but obsoleted hardware that time. The second commercial was like represents you a CPU speed topic, 3.58 MHz(SNES) vs 7.6 MHz (Genesis) which console does have fast processing, SNES or Genesis? You guessed it. Yeah... SEGA's marketing in United States was super genius to drive Nintendo too serious for competition, and it worked.

~Edited with correction~

I'd say we used the number of bits as a serious descriptor in the US until my about the 32 but era.  64 was used, of course, but not to the same degree.  I recall very little talk of bits after that.  

16-bit what though? Typically we define a consoles "bit" by what the CPU is capable of.

And the Turbo-Grafix-16 was technically an 8-bit console by that definition as it had an 8-bit Hudson Soft HuC6280 CPU.

Even the Neo-Geo used an 8-bit CPU as a co-processor with a 16-bit main processor. - So that console can be regarded as 16-bit rather than their rubbish advertising of "24-bit".

Fact is, you can have a CPU that is 8-bit be faster than a CPU that is 16-bit, just like how you can have a 32-bit CPU that is faster than a 64-bit one, it doesn't really define the amount of colours you see on a display. - CPU manufacturers do not tend to invest in pipelining, caches, branch prediction, instructions into simpler 8-bit cores as it's pretty pointless.

The GPU though is really what defines the visual makeup of games that defines a console.. An 8-bit GPU has a fundamental limitation of 256 colours, unless it uses a "True Colour" mode. - The NES had a limitation of 64 colours at once, which certainly falls short of the theoretical capabilities of an "8-bit" GPU.

Megadrive/Genesis has a 9bit RGB colour pallet (Max 512 colours.)
SNES had a 15-bit RGB mode for 32,768 colours, albeit only 256 could be displayed per scene scanline...

Pem, i'm sorry, you shouldn't give me a lot of information much that i forgot to type CPU. Again. Huge sorry to waste your time xD