I chose GIMP to make simple 2D graphics for my game because it's free. I am curious however, how much better Adobe's software offerings might be. In terms of capability, how does Adobe's Creative Cloud software compare to GIMP?

Photoshop is mainly about art and functionality. But you cant make art for 90% of all 2d Indie Games at GIMP. And not apply AAA progs, as Marmoset Toolbag, Houdini, 3ds max, Maya, Zbrush, Substance painter.

Photoshop offers more functions, but GIMP is definitely not bad. Artistic workflows are very similar in both softwares and it comes down to the skill of the artist, not the software. They both have very similar drawing tools and they both have customizeable brushes. There's not much more you need for art, other than knowledge and skill.

But that's solely speaking Photoshop & GIMP. You're mentioning the Creative Cloud, which is an entirely different caliber. Photoshop is only one of many available softwares in the CC. 
So depending on what kind of softwares you need you might be much better of with the Creative Cloud. 

If you just need some 2D illustrations - go with GIMP if you don't have the money for PS (alternatively look into Fire Alpaca (free), or lower budget software like Clip Studio or Painttool SAI etc.).
If you need more than that - look into the Creative Cloud. But there is also a lot of Open Source software compareable to the stuff CC offers, so you might not even need it then.

Personally I use both. I used to only work in GIMP years back for the same reason - no money. And it really doesn't limit you artistically, you can do almost the same things and there's a workaround for pretty much everything. Photoshop (or the cloud in general) does come with some perks like better customer support, regular updates, bigger pool of learning material etc. But it really depends on how much you value these things.
Nowadays I mostly use Photoshop, but that is primarily just because the industry wants me to work with PS. So if you're just making 2D graphics for your own game you can literally choose whatever you want.

I'd also consider that not all softwares are good at or for the same things. So depending what kind of 2D graphics you're making GIMP/Photoshop might not even be your best choice. For that I'd recommend to try a bunch of softwares and see what fits your workflow best.
 

Photoshop is a jack of all trades kind of software, it does everything and it does it at a decent level. Lot's of 2D Indie studios only use Photoshop, and nothing else. Any 2D art, Animation, even some 3D art can be made by Photoshop.

Seamless textures is faster because Photoshop has context removal, and a patch tool that tries to match the surroundings. It has more in depth layer blending tools. It also has a dynamic workflow that allows for changing data of a image, without changing the original image.

It also has much better brush tools and feels better than Gimp when digital painting (yes Gimp 2.10 is better but still lacking) .

To cover all the tools Photoshop has you need: Gimp, Krita, Incscape and Blender. Combine that 4 and reduce the resulting software to 25% of it's power and that would be Photoshop.

The best part of Photoshop is how it works along with other software. Because it can do a everything to a acceptable level, it is good for smoothing out workflows.

Photoshop's trail, it is just long enough to get over the frustration of how different it is from Gimp.

It's not only GIMP x Photoshop, there's tonnnnns of image editors, some are better than others depending on what you want to do (meaning, visual style). A realistic painting app isn't going to be as good with pixel art as a program designed specifically for it.

A nice free generic editor is Paint.NET, it's easier to get into than GIMP in my opinion:
https://www.getpaint.net/features.html