I curious as to whether you chose the ME-80 over the G5n or if you just happened to choose it
I'd taken a hiatus from music for a few years. I'd primarily used single pedals (boutique, mass produced, etc) and liked having instant tweakability. I remembered always wanting a Boss ME-50 back in the day, loving its WYSIWYG interface. Seeing that the ME-80 was out and googling it seemed to say it was a vast improvement over the 50 (and 70) sold me on it.
Then I started frequenting TGP's multifx section and seeing that the collective had lost their marbles since I'd last checked in with them, spending thousands of dollars on their multifx units (rather than the ~500 they were spending a decade earlier). The G5n and Zoom are mentioned as really excellent and, had I known, I'd probably have gone for it over the ME-80 due to increased amount of effects (Boy, would I love that sequencer).
At the end of the day, though, I love the ME-80, it does almost everything I need and it's so tweakable. I went from loving it at first listen, to feeling like I made a mistake as some models didn't behave as I expected, to experimenting more and realizing I had made the right choice as I really learned the nuances of the unit and how to get the tones I want. For example, I surprisingly found the best metal tone on the unit (for sitting well in a band mix) to be the Clean amp model with the DS-1 model

. I do use the tubescreamer model and the boost model, but not at all as I would use a real TS/boost. I do use the Muff fuzz as a fuzz, though!
Another thing that I learned about the unit is that, despite what looks like a static chain (and you can't reorder things) and despite what the literature implies, effect placement is programmed to change depending on the effect selected. So, for example, if you choose the Phaser on the Modulation category, it will jump in the chain to before the amp input.
The G5n is close (may even sound better!) but it still has menus and scrolling. For example, if I want to test some gain staging on the ME-80, it's super easy to compare and contrast instantaneously. The G5n would require scrolling through various amp/OD types before twisting the knobs on the selected units. Additionally, I'm someone who would get lost trying all the different effects, rather than just choosing a tone and playing. The relatively limited palette on the Boss is great for me actually producing music, rather than consuming tones
This is a great video of what the ME-80 is capable of (no post processing done on it!)
Anyhow, way off base. The ME-80 is great for my needs but I can see why many would go for the Zoom instead. And let me be clear, if I woke up tomorrow and there never was an ME-80 and I owned a G5n, I would not be upset as both fulfill near identical functions for my needs.