Is shadow better than sonic
Shadow often claims to be the ultimate lifeform, but his superiority over Sonic is questionable.
The logical place to start would be speed. In Sonic Adventure 2/Battle, Sonic Heroes and Sonic Riders they go the same speed. In Sonic '06 and Sonic Rivals, Sonic is faster. In Shadow the Hedgehog, Shadow is faster. Some of the argument stems from Shadow wearing his air skates- surely he's not as fast without them. Once again, the evidence is in both ways. In Sonic Adventure 2/Battle, he will move his legs just as fast as Sonic when he runs uphill. But he also pants when he runs away with Maria, suggesting such physical activity is difficult for him- but to his credit, we have no idea how long he was running. He doesn't use his air skates in Sonic Riders but his speed rating is just as high as Sonic's. It is also worth noting that the air skates are probably powered by Shadow himself- the fuel would be taken from his bloodstream. Otherwise, he's have to carry two massive tanks of fuel with him wherever he went. Overall, it seems that Shadow is just as fast as Sonic, he just prefers to use his air skates.
Next comes Chaos Control- the power to distort time and space. Shadow has been known to use it without a Chaos Emerald, whilst sonic must have one in his possession or at least something that gives out the same amount of energy with the same wavelength and properties- like the fake on Tails made. Shadow has used it to teleport, freeze time, fly and in a range of defensive and offensive manipulations, like Chaos Blast (it is possible that this and the flying is an effect of the presence of the Black Comet on or nearby Earth). Sonic has used it to teleport alone. It is clear that Sonic has less power in this sense and less of a mastery over Chaos powers.
There are other skills that each character possesses Each have the same move set, but Sonic can also use the magic gloves and bounce bracelet, as well as fly a plane. Shadow has never encountered these two items, and has never flown a plane. He has, however, driven a car, a jeep and a motorbike. He is also a good marksman and swordfighter, although his hand-to-hand combat skills are little more than energy-enhanced punches and kicks- no blocking at all. Sonic has driven cars in spinoff games, but it is unlikely that these are canon. He also refuses to use guns, so he probably wouldn't and has never practiced.
Shadow's claim over being the ultimate lifeform is most likely correct- he bears a resemblance to Super Sonic, like his quills being skyward and his yellow blur when he runs (although this could be due to his air skates). He unlocks more power when he removes his bands, although this leaves him drained afterwards, similar to Sonic when he loses his super form- he has no rings and little energy. However, surely if Shadow is the ultimate lifeform then his energy is limitless. Instead, he can activate a watered-down version of a super form. The same happens when he removes his bands in super form- he loses energy quickly. In fact he loses energy faster than Sonic- he is reported to be weak in the Finalhazard fight even though he doesn't remove his bands until he tries to stop the Space Colony ARK (he does it in Sonic X and probably in Sonic Adventure 2, as Sonic presents Rouge with one of them- so they must have been removed). However, the second time he did this form, he didn't have such effects- probably meaning that it takes a character time to adapt to this power- both Sonic and Shadow look different in their first super forms to their next ones. Indeed, Shadow even learns the light dash faster than Sonic (who required two items to do it manually, whereas Shadow perfected it in one). The only argument that flaws these is that Shadow remarks that Sonic 'may be the ultimate lifeform'. No one knows if he is serious.
Finally, the question usually posed is 'who would win in a fight'. No one knows. Their first fight results in them both fleeing, the second aboard the ARK has no actual conclusion (and in Sonic X, Shadow flees when he realises that he's distracted Sonic long enough for the countdown to begin) and their third fight in the Frog Forrst also has no winner.
So, use this evidence to make your own conclusions.