No. Bishops are slightly favored, but it also depends on the board and their mobility.
Are Knights considered more valuable than bishops?

As with all things in chess, "it depends".
Knights are good in closed positions, where they can dance between pawn blockades and such. Bishops are good in open positions, where they can control diagonals and keep a whole chain of enemy pawns from advancing.
As a general rule, knights are better in the middlegame, while bishops are better in the endgame, but they have their uses in all parts of the game.

When my dad taught me to play chess he always said that late game bishops are more valuable than knights. For the longest time it seemed like everyone agreed with that (at least the people I played against online) but now it seems like more and more of opponents are willing to sacrifice a bishop to take a knight. Is a knight considered more valuable than a bishop? If so why and when did this happen?
In many positions, Giving up a bishop for a knight is beneficial even though a bishop is better.

It depends. bishops are normally better than knights because they can move faster. There are, however, a few situations in which a knight is better, such as this position.
Black is better than White, because although material is even, White's bishop is not doing anything. Meanwhile, Black's knight is a huge threat to White's king.

Knights are only better when you are a beginner. As soon as you reach the stage where you don't think knights are "tricky", you will see that bishops are better in the majority of situations. Knights are very good in tightly closed positions, where bishops and rooks suffer.
When my dad taught me to play chess he always said that late game bishops are more valuable than knights. For the longest time it seemed like everyone agreed with that (at least the people I played against online) but now it seems like more and more of opponents are willing to sacrifice a bishop to take a knight. Is a knight considered more valuable than a bishop? If so why and when did this happen?