Well, Sargeras was better for me because you could read about him in the tomes and other clues in game since vanilla, he was the big bad dude and I feel that he was way better enemy "far far away" than when we actually saw him. Stories about Broxigar, Medivg, artefacts from Warcraft RTS games. Even if the end of him was not that good and they actually made him seem like a stupid giant because he was fooled by Dreadlords and sucked into a ghostbusters trap, while he was unknown dude who was always there - it felt "nice".
Now we have Jailer, supposedly working against us since Titans corruption and so one but it just feels like very cheap "haha this was him all along" trick after pulling out some new character. It's DBZ levels of building