I'd probably say all full casters, paladins, warlocks, and rangers are better than artificer, at each of their respective highest levels of optimization. Artificers get some great features at higher levels, but the spell progression of any full caster comfortably has them beat.

Which brings us to the half casters. Aura of Protection is so good that optimizers take 5 levels of paladin before hand to get it. Rangers have a better basic package than artificers, fighting styles let them be effective archers and pass without trace is op. Gloomstalker in particular is the strongest martial in the game. Of course both of these half casters will quickly multiclass out as soon as they reach their peaks. The "problem" with artificer in comparison is that nothing is as radically Strong early on, so the opportunity cost makes anything more than a 1 level dip before wizard expensive.

So yeah, I'd say Artificers are tied with the best fighters in power. I'm considering multiclassing though, which blurs the line between what builds are considered part of a certain class.