Luigi does better against Oli, Wario and D3 than Mario...if you're looking for a near-perfect fit.
If Mario really suits your particular style though, then definitely go for it. If you're familiar with the matchups for Olimar and Wario, they're both definitely winnable for Mario. The only true issue that Mario has for Wario is actually killing him...As A2Z pointed out, it's very hard to land Fsmash on a wary Wario and Usmash doesn't KO him until high percent fresh. Fortunately, Usmash has decent priority and range in comparison, so it's a decent KO move against Wario for all intents and purposes...besides KOing early XD
D3 is doable if the infinite isn't legal. If it is, Boss told me himself not to try the matchup...and I'd have to agree with him. It's extremely lopsided. If it's not legal, it's still an uphill battle for you, but it's not an unreasonably large disadvantage if you can space well with Mario (Cape, Fireballs, Bair, Dair, Fsmash, Ftilt...all without being predictable).