A lower number means more brightness. All of these are apparent magnitudes. If you mean intrinsic magnitude, the answers are somewhat different. Sirius and Alpha Centauri A are bright because they're close to us. Canopus, on the other hand, is much brighter, but also much further away (Sirius is about 8 light years away; Canopus is more than 300 light years away).
Off subject:
Some planets are brighter (in apparent magnitude) than stars; for example, when Venus appears in the sky, she is always the brightest object (after the Sun and the Moon). In fact, Venus is bright enough to be seen in the broad daylight, if you know where to look. Planets look like stars, but their movement between the stars can be detected if you observe them just for a few nights.
The Sun is the brightest star for us. Apart from the Sun, the next brightest star
as seen from Earth is Sirius.
The sun is considered to be the brightest star in the sky.
brightest star:north star nickname:dog star
the brightest star in a constellation is called the alpha star
Arcturus is the forth brightest star.
The brightest star in Orion is Rigel.
the brightest star in the heavens is Vega
brightest star:north star nickname:dog star
The star Enif is the brightest in the constellation Pegasus.
the brightest star in a constellation is called the alpha star
sun is the brightest star in the galaxy
the brightest star in the heavens is Vega
The brightest star in Orion is Rigel.
The brightest star is yellow.
Arcturus is the forth brightest star.
Rigel is the brightest star in Orion, Betelgeuse is the 2nd brightest
The brightest star in Ursa Major is a star called Alioth.
the blue giant is the brightest star
Sirius is the brightest star in the night sky, but the brightest overall is the sun.