Currently I do a lot of traditional drawing and hand cartooning, but not much in the way of digital. I recently picked up a Surface and have been doing some drawing and painting with Art Rage.

I'm interested in creating art (strictly 2D) for games and I'm wondering what software packages are good for doing drawings and animations for in games and what some of the benefits/tradeoffs of the different options are?

I do have a license to Spriter Pro, but I haven't used it at all, it came with a Steam bundle of some other software I was purchasing. Is this good for creating game animations?

Hello.
I think you can make a broad statement like 'almost everyone that draws or animates for a living uses a Cintiq or equivalent device'. An equivalent device would be a Ugee, for example.
I don't have experience with either.

From the software choices of professional freelancers that I've read (for those that do reveal it), Photoshop is by far the top choice.

For animation it can vary between Toon Boom, TVPaint, Flash etc.
Studios that produce for broadcast use Toon Boom Harmony -- Mercury Filmworks, for example, according to a person that worked there.

Then there's the open-source or cheaper alternatives when you can't afford the industry standard software. For painting, Krita seems to be the closest thing to a free Photoshop. There's some commercial software that are still pretty good, like Clip Paint Studio and Paint Tool SAI (the latter is very popular, it's simple and to the point).
For animation it's complicated. There's obscure products like PD Howler, Animation Paper, Synfig and several others.

If you have clients, if you're getting paid, then you must add the cost of software subscription (like Photoshop CC and Toon Boom Harmony) to your rates.
There's more information here: http://wiki.polycount.com/wiki/Freelance