With each iteration of Illustrator, I'm finding the guidelines fainter, thinner and generally harder to see. I'm speaking of the guides dragged from the ruler or created via Cmd-5. I've tweaked the lines vs dots in Preferences, as well as their colour without any joy. After trying to use what turned out to be a stray hair on the monitor as a guide, I decided I needed to see if an actual solution to make these suckers pop again existed.
It would be really nice to see a screenshot of what you consider "thinner" guides.
I just had a look at the guides in Illustrator CS6 and they have a thickness of 1 px. In Illustrator CC it's the same. (My GPU isn't compatible with Adobe CC so I'm using CPU rendering.)
Since guides can't be narrower than 1 px, it's must be something else bothering you. I suspect it might be the GPU rendering that's causing smoothing of the guides (though I'm not sure).
You can try to turn off GPU rendering by entering Edit > Preferences > Performance and unticking GPU Performance.
I find a straight 0=R, 255=G, 0=B pops pretty well, or I'll switch for a given document to a bright purple if the green is lost on that design, though the old-school cyan is most often OK with me too.
In Affinity Designer, they use a darker hue that still pretty close to cyan - works well too.
Hope that helps.