I posted in another thread, but maybe I should have posted here too.
Yes, cheaters/hackers are everywhere in MP.
But with the right cars, you can beat a lot of them, as they are usually extremely bad drivers.
Bronze league: Your best option is the Lotus Elise, or any other D class with long nitro.
Silver league: I only use 3 cars there, namely the Viper ACR, H2 Speed and Acura NSX. I tried many other cars, but only those 3 take me to Gold league quickly. Plus, they are easy to get.
Gold league: Here, you need good cars, fully upgraded (with epic parts if possible, although this is not mandatory). My best options are, by order of preference, the Huracan Evo Spyder, the Corvette GS, the SIN R1 and the Ferrari F12.
The Aston Martin DBS Superleggera, Vantage GT12, Mercedes-Benz SLR McLaren, Porsche 911 GT3 RS and Porsche Carrera GT are other good options, but they are difficult to get (mine are still at a low level, so I don't use them).
Platinum league: Things become harder here. The Pagani Huayra, Lamborghini Aventador J, Porsche 918 Spyder and VLF Force V10 are very good here. Note that the Huracan Evo Spyder, Corvette GS and SIN R1 are also excellent choices in this league.
Other cars seem to be good options, as they give me hard times, but I don't have them or at a low level, so I haven't tried them: Techrules AT96, Genty Akylone, Ferrari LaFerrrari Aperta and Corvette ZR1.
Legend league: Ouch! The top S class cars are a nightmare to get and upgrade... The Lamborghini Egoista performs well here. Honestly, I find the Vulcano and Lykan totally useless. So I won't recommend any S class car here (apart from the Egoista, as my few top S class cars are not upgraded enough to compete.
However, there is still hope. Pagani Huayra, Lamborghini Aventador J, Porsche 918 Spyder and VLF Force V10 are very good here. Note that the Huracan Evo Spyder, Corvette GS and SIN R1 are also excellent choices in this league too.
The cars shown in bold characters are those I use in MP (maxed or nearly, with or without epics installed). So believe me, they work very well. I always reach the Platnium League, sometimes the Legend League when I decide to put the time and effort necessary, and I always easily reach the top 3,000 with those cars. And this despite those pesky cheaters/hackers. And I don't need to **** or hack.
By the way, before you call me an Alien or whatever name, I am a TouchDrive player only...