I wouldn't call Nintendo 64 a failure in terms of sales - though it was the start of a downward trend for Nintendo on that front (a trend only ignored by the Wii).

The actual console itself is of course, heavily overrated due to the amount of people who wear nostalgia goggles when looking at it. From a rational perspective that's not clouded by nostalgia (being as I never owned an N64 as a kid) it's an ok console with ok games. The only N64 game that I've played that truly holds up today is Ocarina of Time. As for the rest of them, I'm sure they were all great in their time period but they haven't aged well (and I've played most of the beloved N64 games, with the notable exception of Majora's Mask).

Don't worry Nintendo 64 fans, the Gamecube is even more overrated!

OoT I'll give you, but mario 64 and especially goldeneye are vastly overrated.  Mario 64 I give some leeway too since it paved the way for things to come with 3D platformer games, and at the time it was good but mostly because it had nothing else to really stand against.  Mario 64 doesn't stand the test of time but it's not alone in that regard, the fifth generation in general has aged like a loaf of bread left behind a leaky water heater.  And goldeneye, ugh, just hearing the name makes me want to vomit, but I grew up on pc fps games, so I suppose I have bias, but I still can't touch a console fps, the mouse is too perfect. 

And really, the gamecube is too much of a failure to be overrated.  At worst it's cult.

I personally felt that the N64 was a lousy console with a laughably stupid controller and a pitiful selection of games compared to its predecessors. To be perfectly honest I'll never understand why the system receives so much praise. Additionally, as many other posters have already pointed out, the N64 did not come close to outselling the vastly superior Genesis.

Who ever called it a failure? Sony fanboys?

failed to keep up with the competition...

but their games aged better than the ps1 games I must say....

Who cares? The console is 20 years old...

As someone who is commonly mistaken as a Sony fanboy (I actually just Hate Xbox), I can say that I don't think anyone really considered the N64 a failure. Just a loser, because it didn't win it's generation. Second Place is still good, though.

http://romhustler.net/img/screenshots/psx_full/ingame/4fca1aaf87a20.jpg

Looks pretty good to me, even though IX is awful.

I don't think they did in terms of gameplay. A lot of N64 games has terribly clunky controls and feel downright awkward to play these days. The same can be said for many PS1 games but it also has far more RPG and TBS games that still play really well today.

It wasn't a failure but was the start of Nintendo's downfall for home consoles.