I tried out most of the standard bases that GAMESS offers without any extra functions. The input looks like this (enter the base instead of ***). After evaluation I extracted the information with Visual Basic.
! Ethane staggered
$CONTRL SCFTYP=RHF RUNTYP=Optimize $END
$SYSTEM TIMLIM=30 $END
$BASIS *** $END
$GUESS GUESS=HUCKEL $END
C 6.0 0.0000000000 0.0000000000 -0.7688320347
H 1.0 -1.0157199281 0.0000000000 -1.1532895468
This is the result. You see the C-C and C-H bond lengths (in Angstrom) and the C-C-H angle. The table is arranged according to the complexity of the base (information). In the first line are the literature values , in the other lines relative deviations.
The first three are semiemperical methods. They show the worst results (as it is supposed to be).
It's more difficult to say things about the ab-initio calculations. It can be seen that bond lengths never differ much more than 0.01 (which is nice). Another interesting fact is that with a better basis, bond lengths tend to be shorter . At the HF-SCF limit (self-consistent eigenfunctions of the Fock operator) bond lengths are usually too short (which is not nice). This is just shows a limitation of the method. Sometimes medium sized bases give better results than large bases. To overcome the problem, you need correlated calculations.
Lide DR. Handbook of Chemistry and Physics 86th Ed. 2005-2006. CRC
Kutzelnigg W. Pure appl. Chem. 49, 981 (1977)