Three fluted drills make triangular holes, two fluted drills make oblong holes.
Seriously, it is impossible to drill a round hole with any standard drill bit. There are all kinds of fancy drill bits available, like "core" drills, double margins, etc. that drill "rounder" holes, but reaming is the best way to get one as round as possible with normal drill presses or hand held drill motors.
You can actually do pretty good with a standard bit if you start with a pilot hole to keep the center of the bigger bit from doing any actual cutting. When the center is cutting is when it tends to walk around a bit.