The best replacement for mapbox is google maps.

The best alternatives to mapbox are rated as following:
★★★★★  google maps
★★★★★  leaflet
★★★★  tilemill
★★★  mapkit
★★  openlayers
★★  cartodb
★  openstreetmap
★  arcgis

Your alternative for mapbox is not listed? Suggest!
Speaking about mapbox, one probably shouldn't forget about openlayers.

Other search terms related to mapbox and their ratings are:
★★★★★ openlayers
★★ leaflet
You have in mind a companion for mapbox and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of mapbox in all years. Click on graph for more.
mapbox
google maps
leaflet