It's important to know the difference between attacks.
As you may have noticed, Pokemon Go supports real time battles, as in the previous Pokemon Games, the battles were round based (so one attack per round). The initial Speed attribute of Pokemons was used to determine who gets to attack first. In Pokemon Go this is missing.
The main difference to Pokemon Go is, that in Pokemon Go attacks also have a certain amount of time that they consume.
So i.e. the attack scratch was usually 40 dmg and 100 accuracy in the first gen, a not-very-useful attack. In Pokemon Go, Scratch does have a very good 12dps (damage per second). --> The usus is to take the dmg an attack has and also the time it uses.
So don't get confused over the bare valuet that's written at the end of the attack, important is its dps.
For a complete list, you may want to checkout this website which contains a list of all Pokemons, which moves they can learn and how much dps each move deales.
TL;DR In Pokemon Go efficiency of attacks are calculated as dps (damage per second). The faster an attack is, the more often you can spam it and therefore attack and it's speed matter.