G1 Sideswipe = The first production run sold out despite widely reported paint issues which were said to have been caused by Lamborghinis insistence that the toys be painted with the exact paint used on their cars. Secondary market prices reached ridiculous levels until a second run was announced.
Red Alert = Also got a second production run.
After this Takara upped the numbers on their initial runs of new molds to meet the demand. Carbots were selling beyond their expectations.
Tigertrack = Has a lot of history dating back to the pre-G1 Diaclone era,
Who Is Tigertrack? – Part 1 | Source Blog
The primary appeal of Tigertrack would be to Asian collectors, that's why it was a limited release Tokyo Toy Show Exclusive.
G2 Sideswipe = Every other black repaint Takara have done has sold well so it was a no brainer. Like Red Alert it has some retooling so it's not a straight repaint. It's been popular enough for Dr Wu to make an add on set for it.