Both of my girls needed some kind of a big deal at that age to help it sink in. For my oldest (she was 3 at the time) she really wanted to go to preschool and I told her she couldn't go until she was using the potty all the time (excluding poop issues, but that came about a month later). 2 days later she was fully pee trained. Just stickers and candy wasn't enough to end the power struggle between her and I.
My 2nd DD was (just shy of 3) almost the same, more then capable, but just not wanting to. She also wanted to do what the bigger kids were doing and move to the preschool room at church and I wouldn't let her till she could use the potty. Also we planned a big kid trip with their grandma and cousins to a fun place and I just told her grandma wasn't taking kids in diapers (we had her little brother in diapers). Again within a week she was fully using the potty. Stickers and reward charts, even m&ms have never been effective incentives for my kids in regards to potty training.
We will see how this goes with #3, at this point he seems way more interested then either of the girls did.
DD1 (7) DD2 (4) DS1 (22 months) Baby #4 EDD 7/13/14