There are an infinite number of points in a line, and an infinite number of points in a plane, whether the line / plane are bounded or not. So the only question is how do you compare their infiniteness to each other?
From what I remember of number theory, the set of real numbers is an uncountable infinity. The number of points in a bounded line maps to the set of real numbers. The number of points in a bounded plane seems (without giving it much thought) like it also maps to the set of real numbers. I would guess that they have the same sort of infiniteness: uncountable infiniteness.
This kind of thing can be counter-intuitive. Like, if you compare the set of all integers, with the set of all even integers, it turns out they have the same size; they are both countably infinite. "Size" is defined differently for infinities than it is for actual numbers.
("Countable set" means that the set can be mapped to the set of natural numbers.
http://en.wikipedia.org/wiki/Countable_set )