One thing I realized upon viewing the flash animation, is that Marvel would basically be all within one tenth dimensional boundry, same for DC, each one would be a tenth dimensional object. To see there are other omniverses would imply that there exists 13 dimensions at least based upon that premise within the comic book worlds.
Here are where I would rank the characters based upon the flash animation:
*) Silver Surfer (has time travelled before)
5th dimensional - reasons being that he has time travelled before to the past, and then come back to the future, which would imply ability to move along the 4th dimensional line. He has also mentioned being able to travel to anywhere he's been before, including pocket universes, and the realm of Chaos and Order for example. This would place him as having the potential to be 5th dimensional, but having only barely tried to use that potential.
*) Franklin Richards
6th dimensional - he has travelled to a timeline world where his unborn sister grew up and saw her, even though she died in the current timeline. This would place him firmly in the able to go to and see alternate realities that are disassociated with the Marvel 616 timeline.
*) Superman One Million, who has punched through time
6th dimensional - able to punch through the wall of time while in a weakened state, to a reality which may have not been the same timeline from which he came from and existed within. To top it off has inheritance from imps within his blood making him extradimensional in nature. 6th dimensionality is the most he has demonstrated of his powers; his true power may be beyond that.
*) Gog from Kingdom that travelled back in time to kill Superman
6th dimensional - was able to travel back in time and kill Superman over and over. In the process of doing so though he would have altered his future, which which would really mean that he was hopping into another dimension (alternate timeline) in order to do so.
*) Kosmos / Beyonder / Molecule Man
8th dimensional - They were able to travel outside of Eternity / Infinity (outside of our known universe) and travel into the beyonderverse which exists outside of space and time. True Beyonders would be 9th dimensional.
*) Waverider
7th Dimensional - able to travel to any alternate timeline within the DC Universe.
*) A Celestial
Unknown.... if they are advanced cosmic cubes, then it would imply they are related somehow to the true beyonders, which would imply 9th dimensionality. They haven't demonstrated any such ability however. This may or may not be due to self-imposed limits placed upon their physical bodies; their true forms may be more powerful. They do seem to exist in all realities throughout the multiverse however.
*) Universe 616 Eternity
7th Dimensional. Contains all possibilities for one universe.
*) Multi-Eternity that houses 616 Eternity:
10th dimensional. Contains all possibilities of all universes.
*) Mad Jim Jaspers after creating his own universe
7th dimensional being, possibility of expanding into 8th dimension.
*) Omniverse Merlin
Was demonstrating knowledge of the tenth dimension, possibly higher. Shown to operate within 9th dimensional boundries as he was freely able to move between actualities. Hinted at being more, since he was aware of there being multiple multiverses throughout the omniverse.
*) Parralax
Demonstrated powers of 8th dimensions. Capable of creating / destroying universes and travelling backwards and forwards in time.
*) Classic Ion
I would say 8th dimensions. To a higher degree of power than Parralax. Similar to how not everybody is created equal, both Ion and Parralax were capable of operating within 8th dimensional boundries, but classic Ion was clearly above Parralax.
*) Extant
8th dimensional, maybe 9th dimensional?
*) Abraxas
9th dimensional, and a powerful 9th dimensional being at that, as he was affecting infinite universes at the same time.
*) Living Tribunal
10th dimensional. Able to preside over the multiverse and recreate a universe with but a snap of his fingers, still exists under TOAA and still apparently has limits, as shown when Thanos absorbed him with the HOTI and showed that there were alternate multiverses outside of the multiverse which contains universe 616. Maybe even 11th dimensional, but he has his limits although they seem to be above multi-Eternity.
*) Marvel and DC brothers
Seemingly they would each be ten dimensional points, so being able to exist on the same plane would imply that they were 12th dimensional beings.