Can't go wrong with an alpine tbh
Other than that the usual suspects are clarion,pioneer and kenwood
The new pioneer systems are supposed to be really good,but alpine would always get my vote.
Depends more upon how much you want to spend.
I have a Kenwood DNX with all the bells and whistles.. it is superb and dare I say.. Better then the Alpine rubbish I have bought in the past, I will never have Alpine again.. I bought the top range Alpine touch screen for use with Iphone and it was just a pain to use, and the bluetooth was dogged with software issues.. Just my experience with Alpine.. The Kenwood is a pleasure to use..
Everyone has different opinions,I worked in the av industry for 4 years and over those years alpine came out top of the pile every time. But as I say,everyone has different experiences with these things,the new kenwood stuff looks pretty sharp for the money tbh