I agree with Patrick in general, what I would is that there a different ways to quantify success (second part of the question).
In terms of pure innovation (a new product) the success rate is low. If you look at the number of products still in market 4 years after launch anything above 10% is pretty good.
For incremental or replacement innovation (a new flavour, or having an updated version of the old product) it is much higher. This makes sense though as you are forced to buy the new product as the it is replacing the older one, hence it only fails if the established brand disappears which is relatively rare.
Also note that some incremental innovation is only designed to last for a short amount of time, if you look at snacks the big brands always bring out new flavours to keep consumers interested, but these only stay in market for a season, or maybe a year at best. Supermarkets don't have space to stock everything so they keep the innovation cycling through.