why did they never make a gamcube gta game i mean xbox had it ps2 had it so why no gamecube versions?

different audiences, different games

CG disc max capacity = 1.5 Gb
PS2 disc max capacity(single layer) = 4.3 Gb

Thats the reason...

Nobody but Rockstar knows for sure. I've heard all manner of excuses (they couldn't meet Nintendo's quality requirements, the game wouldn't fit on a single GC disc, there weren't enough buttons on the GC controller, the majority of the GC target audience didn't play GTA, etc.). But I've heard no definite word on if any of those reasons have been cited by Rockstar itself.

they still could have done 2 discs

In fact sould be 3 or 4 discs, can you see a game like SA in three mini dvds??, one for each city, changin disk to move from town to town, (And this is the best case scenario)... maybe they saw the GC sales vs the PS2 sales, and they thought it didn't worth it...

Let's put it like this: Name two Rockstar games for Gamecube. See?

There were many rumors back in the day that suggested that Rockstar only wanted to produce a PS2 versions of the games but Microsoft paid for XBox ports (which made PC ports easy) and to ensure the Gamecube did not receive a version.

I want one for the Wii.

That only applies to San Andreas. A report of ISO game sizes on the Xbox said that III and Vice City were 700MG and 1.2GB respectively. That's certainly not too large for the GC.

It was Rockstar not wanting to bother, plain and simple. Bully is apparently testing to see what they can put on the Wii.