Shonda,
I had a HARD time with my now 2-year-old daughter, as well. She was dead-set against sippy cups of any kind, it seemed!
I finally got her to take the Nuby soft-spout bottle, after trying about 47 kinds. It was kind of a nice in-between cup and bottle for her. But then, she started fighting that one, and we switched to the Nuby hard-spout cup, with the white filter thing that lets you switch between fast and slow flow.
I liked that all the Nuby cups were pretty cheap, but colorful [not cheesy], and at that price, I could afford to try a couple of different options for her.
In terms of whether your child even wants to try a cup yet [because sometimes, they just get stubborn and won't do it], does he ever try to drink from a straw? Does he try to drink from a regular cup? I found that talking up the "big girl" ["big boy," in your case] aspects helped more. And talk to your pediatrician and/or day care teachers [if he goes to day care].
When it came time to switch, my daughter's day care teachers just went cold turkey on her - they said she'd keep taking the bottle if I let her [which was true]. And her doctor said the same thing. The thing is, at your son's age, he'll take the cup if he's thirsty - he's just hoping you'll buckle and keep giving him the bottle. :)
I'd check with your pediatrician, just to be sure, and once you make the decision to switch, let everyone who might takes care of your son know, as well, so that there's consistency. He'll switch, and even if he throws a fit for a few days, he WILL get over it, and a week later, you won't even hear about it anymore.