Well you could first off sit in a car that you THINK might be comfortable enough (in the showroom) and then compare that car to the measurements offered at www.edmunds.com, in the "new car" section. Then click on "comparisons"
This will allow you to compare up to 5 vehicles. once you've plugged in info on all five, hit the "specifications" tab and it'll show you all the interior measurements of all five cars!
CAUTION: Specs are just specs. Every body is built differently. You might have long torso and short legs, or vice-versa, so even though leg room is the same for two cars, they might still feel different to you, depending on seats, headroom, shoulder width, etc.