Metatrader is, by far, the most popular platform for developing EA's. If you have worked extensively with any programming language before, MQL is not at all difficult to learn/master. Best way to get a feel for the language is to look at the source-code for any of the indicators and EA's that are supplied free with Metatrader. Just use the MetaEditor (found under the 'Tools' tab) to open any of those .mq4 files.
You won't be able to look at the code for most commercially marketed EA's, as those are supplied in compiled code (.ex4) that cannot be read.
Now, that was just the part about the programming language. As for developing a successful EA, see Elkart's comments.