[Trigger warning: If discussing history in regards to a fantasy show bothers you, skip this post] This went a wee bit longer than I had planed, but I like history, so eh...
It really depends on the time period and the compositions of the armies. This fantasy series is based on medieval Europe, around the time of the first and second crusades, from the looks of the game and what I could see in the trailer. For much of medieval Europe, in an open field battle, heavy cavalry was king. For sieges though, they were little better than any other heavy infantry unit (and there were a lot of sieges). It wasn't until armies started incorporating companies of pikemen (late middle ages) did the tactics start to move away from the heavy cavalry.
Here are a few examples in brief (that I vaguely remember and could look up):
The Umayyad Caliphate cut through the Visigoth, who used European Infantry tactics of that time (720s), of Iberia and into France with an army composed of almost all heavy cavalry; until finally stopped by the Franks at the Battle of Tours (732) (by infantry and new/superior tactics, as well as various other factors). It took some time, but the European kingdoms eventually adopted and developed heavy cavalry, to the point that some battles became cavalry charges vs cavalry charges.
At the Battle of Tinchebray (1106), Robert, Duke of Normandy, to start his attack, ordered his heavy knights to charge King Henry I of England's line of infantry. Unfortunately for Robert, Henry's infantry front line were dismounted heavy knights, and were able to push back the attack.
At the Battle of Bremule (1119), King Louis 6 of France, to start his attack, ordered his heavy knights to charge King Henry I of England's line of infantry, but guess what? Yep, Henry had dismounted his knights for the front line, and they pushed back the attack. Now, why would Louis do this, when it had been 10 years after Henry defeated his brother with the same tactic (which the French would have know about)? Because these battles were the exceptions, rather than the rule.
At the Battle of Carrhae (53 B.C.E.), the Parthians charge the Romans (who were in a defensive square) with a line of Cataphracts (heavy cavalry) and backed up with a whole mess of mounted archers. The Cataphracts hit and disengage, while the mounted archers endlessly pelt the Romans with barbed arrows. The Romans are annihilated and the "great" Crassus is no more.
At the Battle of the Axona (57 B.C.E.), the Belgae sent a contingent to flank Caesar's fortified position by fording a river and attacking his rear guard & supply line. Caesar sent all of his cavalry and skirmishers to oppose the crossing. The Romans obliterated the Belgae at the river while the main body of both armies stared at each other all day, north of the ford. Even though they still outnumber the Romans, that night the Belgae war counsel decides to head home.
At the Battle of Dhi Qar (609), the Sassanid army's front line was entirely composed of cavalry, as it charged the Arab infantry and dismounted troops. The Arabs held fast, which allowed for some hidden Arab cavalry to charge from the rear and wipe out the Sassanid leader, along with all surrounding units, causing the rest to route.
There are various other battles with cavalry used to lead the main attack, on the center, against infantry, such as the Mongols and even occasionally Alexander's Companion Cavalry, but I should probably stop there.
Watched only 15 min (stupid work) but it feels like the Witcher universe. Very first scene in the bar happens to you constantly in the game. And there are titties like 10 min in.