Most of the time your not even seeing anything but the jean or dress pant fold caused by the position/zipper/button. Not to mention temperature or adrenalin, or anything like that; could effect a guys size. Its also fairly different from flaccid to erect. Some grow a lot, some grow a little, some barely even grow. So no seeing a huge bulge in a guys pants does not = big penis or the equivalent to what's inside there, because pants do add padding and make it look thicker and a bit longer than it really is. Tho, I don't even know why you would ask this question other than you are curious and want a boyfriend with a big d*** and therefor, would be lying about your preference, otherwise you wouldn't have mentioned that fact or worded the question the way you did ... just saying.