Glaives and halberds are the most effective weapons if you want pure damage output as they have a d10 damage dice, are compatible with Great Weapon Master, and have the reach property. The only downside of these is the two-handed property which restricts access to a shield. If you want to go for a more defensive build, a spear combined with a shield is a great option. Remember that the spear won’t give you access to the 10ft reach, which makes the Polearm Maser + Sentinel combo so effective.
Pikes are the least effective because they cannot be used to perform the bonus action attack.