I shall attempt this as best I can.
Main Timeline
Ultraman
UltraSeven
Return of Ultraman
Ultraman Ace
Ultraman Taro
Ultraman Leo
Ultraman 80
Ultraman Mebius
Ultra Galaxy
Ultra Galaxy NEO
UltraSeven's time line (As Seven exists in his own little universe separate from the rest of the Ultra-verse, while also existing in the primary universe. It's weird)
UltraSeven
UltraSeven 94 (two parts)
UltraSeven 98 (Four parts)
UltraSeven 99 (I want to say Six parts)
UltraSeven Evolution (2001-2002)
UltraSeven X (Possibly included in the main time line as well?)
Then we have Max's confused confusion, which basically goes-
Kinda Ultraman
UltraSeven maybe?
It has some vague elements from Ultraman, though generally Ultraman didn't happen in Max. UltraSeven had to of happened in some fashion though, as one of Max's episodes is a direct sequel to one of Seven's. So you're guess is as good as mine.
Moving away from the Showa continuities, we have the duology of the 90s and a crap ton of one offs.
Duology-
Ultraman Tiga
Ultraman Dyna.
One Offs
Ultraman Powered
Ultraman Great
Ultraman Gaia
Ultraman Cosmos
Ultraman Neos
And the last two that connect are...
Ultraman The Next
Ultraman Nexus
The Next is a kind of prequel movie for Nexus, though you won't realize that until you watch Nexus.
The one offs have nothing to do with one another or anything else, though apparently an AU Zoffy exists in Neos.
So not too complicated, but still a bit odd with Seven giving the greatest amounts of headaches.