Depend how much you are paying for your hosting.
For example, if you are paying 1$/mo then 97% is perfect.
"Usually it's 99%. But let's be honest, it's probably just marketing."
Well, pardon me, but I do not agree with you here. We have 100% uptime for Q4 2017 Q1 Q2 Q3 of 2018 and yes it's possible when as provider you reinvest hug % of your profit for new hardware etc.
Sad but true.. most of the well known providers are NOT reinvesting back.. (something that can be confirmed from the used hardware which most likely will be older than the average).
Again, OP, if your web hosting is cheap then 97% is perfect!