Again it isn't since it was released alongside the original SRT4, competed and did poorly.
It was released alongside the Neon SRT-4, it drove a lot better with comparable handling to the Neon SRT-4 while being slower (but still not giving up much of anything to the later Caliber), and then the Neon SRT-4 was gone almost immediately. It competed well in contemporary reviews, with raw performance favoring the Neon and most other things being better in the Cobalt.
Whining about how it can't be a successor because it was briefly sold at the same time before being sold for another
four years after that (with a six month break for a model changeove) is so pedantic that it amounts to meaningless white noise.
Dodge also offered the ability for buyers to purchase staging upgrades that were full warranty
So did GM.
Yet still competed safely with the Cobalt SS turbo
No it didn't. The Caliber
was a pig. It was a slower car than the Neon SRT-4 and the Cobalt SS turbo, and was marginally faster than the original Cobalt SS. It drove like a truck with its fake LSD and piles of torque steer and tall body and bad ride control. It wasn't in the timezone of popularity of the other two or the competing cars from other brands even in a segment that was waning. The secret was out about it immediately after launch that it was a worse car across the board than the car it was replacing (just like the regular Caliber was), and despite all the great sales and hype that the Neon version had and the super cheap price the Caliber model started at was immediately dead in the water.
The Cobalt SS Turbo, in comparison, was a much improved version of a car that the car rags
already at least liked, and was sold for several years after Dodge immediately cancelled the Caliber SRT-4. Connect the dots yourself.
Car and driver did a detailed break down of the Caliber and it's refinement as well, to indicate a different SRT4 but one offering good performance still. And a decent hand off from the last version in the neon.
Car and Driver also did a detailed breakdown of the Cobalt SS and raved extensively about it being an across the board improvement from the original car. And kept testing it repeatedly. And brought it to their Lightning Lap events and heaped praise on it there. And kept putting it in comparison tests. Like one where they said this about the Caliber:
What these cars don’t share is torque steer, something that makes the Caliber SRT4 nearly undrivable at full tilt but is pretty well eliminated by suspension and power-steering tuning in the Cobalt SS. And the Dodge features neither launch control nor no-lift shifting.
And this other one:
In contrast, the Dodge Caliber SRT4’s high center of gravity, persistent body motions, and understeer made it a challenge to make the most of its 285 turbocharged horses. Not helping the cause was an open front differential that resulted in one tire spinning madly whenever the engine was sucking in boost. Lapping the Dodge was an exercise in managing understeer; no other vehicle abused its front tires as sadistically as the Caliber.
This sentiment was matched by the other rags of the time, some which even called the Cobalt class leading and didn't even bother putting the Caliber in comparison tests.
But yeah, the Caliber "competed safely with the Cobalt SS Turbo."
Between Meh and Alright. 
