Hi there folks!
It's been my personal goal to try and make a cohesive DQ timeline using as many games, novels, manga and other media set within the DQ universe, and some time ago I came up with this "definitive" (at the time mind you) theory.
Seirei Rubiss Densetsu, Item Monogatari, Hero Abel, Emblem of Roto and its sequel, and DQI to XI (sans IX and X) and other things were put into it, using in-game elements/lore/stories etc.
It's not perfect, there's also some personal interpretation of some elements (mostly about XI) buuuuut I'm rather happy about the result.
Hope you'll enjoy the reading of it!
(I shared this theory on the Game Theorist Reddit 3 months ago https://www.reddit.com/r/GameTheorists/comments/jz0ynm/dragon_quest_timeline_proposition/ based on what I previously wrote on some various articles for Dragon Quest-fan, a French website.)
Again, I hope you'll enjoy the read. I'd also be super interested in hearing your take on the franchise timeline. :D
PS: needless to say there are spoilers for the entirety of the saga in it :'D