I find the worldbuilding in Erikson is impressive in its breadth, but lacks true depth. We never feel the vast echoing passage of time in the Malazan novels that you do whilst standing in Moria in Lord of the Rings or in the Nightfort in ASoIaF, in Shadar Logoth in The Eye of the World, or descending into Golgotterath with Seswatha in the flashbacks in Prince of Nothing. Erikson hurls numbers around - this event happened 300,000 years ago, Kallor is over 100,000 years old - but it never feels real. It's just numbers on a page.
The Malazan Book of the Fallen is a great, swashbuckling, high-magic series which is structurally ingenious, has an impressive breadth and intriguing ideas. It's also inherently unrealistic (this planet should have been reduced to dust aeons ago given the powers these races and individuals wield) and fundamentally unbelievable, which reduces its impact, as does its mild similarities to Dungeons and Dragons.
He also lacks an eye for detail. After appearing as a major character in four books we only found out how tall Karsa was when someone asked Erikson in an interview. His timeline makes almost no sense. Whilst the little details can be avoided I think even the casual reader may be pondering why it took a group of characters over a year to travel about five hundred miles across easy, open terrain without major obstacles.
Erikson is one of the better epic fantasy writers out there, but in terms of evoking a true sense of a time abyss (to use a Clutism) or bringing his cultures to real life, he comes painfully far behind Tolkien, GRRM, Bakker and even Jordan (whilst still way ahead of Brooks, Goodkind, Eddings or Feist, naturally).