Three teams have separated themselves from the rest. After that it just depends on what criteria you are going to use to judge the greatest of all time.
HHWC - 3-peat in modern sim with incredible parody. 1 other silver from appearance in the first season! Been demoted once.
Valhalla - 3 peat, 59-1 along the way. Most dominant team ever, hands down. Gutted after 3rd win. (could be seen as positive or negative). No demonstration of sustainability. Less parody.
Hali - Won first two WL titles when teams were much less familiar with each other and much less used to gameplanning every 2 days. Has been in the WL from the start and stayed in the World League for 8(?) seasons now.
In terms of relative to competition, I would say Valhalla, HHWC, Hali.
I can't decide on an order for most impressive accomplishments.