What are your favorite long fantasy series and the most underrated?

I'd consider long to be close to 2 million words or more. Also considering subseries to be all part of one series in that world. Like Realm of the Elderlings with its subseries, and one that's now past this length the Osten Ard books by Tad Williams.

No bias for or against popularity when talking about your favorite. RotE and Osten Ard as mentioned. The Wheel of Time, Malazan, The Wars of Light and Shadow, Discworld, The First Law, A Song of Ice and Fire, Dresden Files, the Cosmere, Shadows of the Apt, Riyria, etc.

What are your personal favorites and what do you think is the most underappreciated?