Needles in a haystack.
For every major author to rise from the kindle there are thousands upon thousands you've never heard of. (But that's sorta true about mainstream midlist authors as well.)
When you selfpublish you are responsible for all of the things a traditional publisher would take care of: graphic design, revisions, quality control, marketing, distribution, etc... but without the sort of resources that a big publisher has at their command. You can cut corners, but keep in mind that you don't get a second chance to make a first impression on readers.
If you selfpub because your dream is to see your book on the shelves of your local Barnes & Noble or on the New York Times Bestseller list, well... it won't happen. Not unless you get picked up by a reprint house. I'm not being a negative cheerleader here, it's just not possible. A little guy can't offer the brick and mortar booksellers the same sort of discounts and deals that a publishing behemoth can offer. It's these booksellers who drive the bestseller list.
But there are many advantages to selfpubbing. You have complete creative control, you have a faster turnaround time, you set your own price, and you don't have to worry about your book being remaindered or going out of print. Plus it's great if writing about something publishers don't want to see, but you're pretty sure reader haven't gotten enough of. (Vampires anyone?)
If in doubt, keep querying.
