Any tire is better than the OEM Continentals! I have a set of General UHP tires. For the price to performance ratio they perform as advertised, and I would consider buying them again.
As mentioned, air pressure is key to mileage, braking, and handling performance. Some tires recommend inflation pressure in the 40psi range. GM OEM pressure is 32 I believe for the tires that came on my G6. The OEM Conti's were OK, but came alive when at 38psi (rated at 44). However, they became hard and sloppy as the tread started to wear off when driving on any roads that were not completely dry.
'11 Ram SXT 4x4 quad cab - 5.7L V8; 128,200kms
'09 Malibu 2Lt 3.6L - 140,000kms purchased 1 March 2019
'06 Pontiac G6 GT - 3.5L V6; 162,000kms (rear ended 15 Feb 2019, and given totalled title by insurance)