Current geocentric distances in AU: (distance from earth)
Venus: 1.29 (radius 6050 km)
Mars: 2.07 (radius 3400km)
Jupiter: 4.16 (radius 69910km)
http://www.planetary-aspects.com/curr_asp/curr_posns.phpradius / distance
Venus: 4690
Mars: 1643
Jupiter: 16805
keep in mind that this changes every day.
this seems to suggest jupiter would look ten times larger than mars and venus around 3 times larger than mars and 3 times smaller than jupiter.
HOWEVER*
this does not take account into the brightness of the objects.
you might be able to see Venus and Mars, but they might be so dim you won't notice them.
We can calculate the brightness of venus, mars, and jupiters, but because they orbit the sun like we do they have different phases like the moon and distances.
brightness comparison:
Mars: magnitude +1.23
Venus: magnitude -4.01
Jupiter: magnitude -2.67
this suggests that venus is twice as bright as jupiter and mars is 30 times dimmer than jupiter.