There are event you can predict on that even though it's not 💯 guaranteed that you're going to win, a level of certainty makes you think that you're surely going to win.
The downside of that feeling is that you might become over confident to use a big amount in the game since you're to a large extent certain that you're going to win.
Can we still say we are gambling if the event is something we are at least 90% sure that we are going to win?
First of all there's no sure win or guarantee win when it comes to gambling or betting but you can use the term higher percentage chance, if at all there's such a thing like sure game as you said, Them most gambling companies will have folded by now, because someone will just sale his land or house and even put all the money they have and bet on that sure game in order to make a return and will continue to do it over again, so far no game is fully guaranteed of the outcome that makes it remain gambling, wether 90% or 99% chance of winning.