In my own opinion, traditional radio button lists are becoming obsolete. And right fully so.
Radiobuttonlists have two qualities: They show all of the options, and they allow only one selection. Dropdowns allow one selection but are compact and slow. Consider that it takes two clicks to make a selection: one click to open the drop down, and another to select desired option. Checkboxes show all of their options as well, however by default functionality, allow multiple selections. We can programatically allow only one selection, but this is beside the point.
Radiobuttonlists are ugly, unasthetic, and a pain in the rear. There are some lists, but few, where you can click anywhere on the selection – text, bubble, or surrounding area, and it magically selects your item. However, for the majority, you have to find the item you would like to select by reading all of the items, locate the corresponding circular radio button, and then click with precision into the 12 x 12 pixel area. The selected choice is then distinguished with a tiny 8 x 8 black circle in the center. Not to mention, how does one ‘unselect’ a selection in a radio button list? Without special programming, you don’t.
Let’s consider the way the modern web works. Users have a short attention span, they don’t want to ‘do work’, and nor do they want to think about the work they are doing. The more intuitive, less work involving, and less work looking a web activity is, the more likely they are to complete it. Thus, we usually want small, compact forms for our users. Because, the less the user has to ‘do’, the more likely they will complete the task. The only exception to this rule is when we are emulating standards that have already been set – for example, an online poll is a vertical-itemized radiobutton list with a ‘submit’ and ‘view results’ button. We don’t want to reinvent the wheel, but we can alter their training on a very similar, perhaps easier, wheel.
Take a look around at what alternate control sets are being pushed out onto the web, Survey Monkey, for example, has some great ideas. On-hover colored, and quite large, they are easy and intuitive to use.