In most cases Lava is much hotter than fire.
Lava can sometimes be hotter than fire and sometimes it may not be as hot as a fire.
It depends on how hot the fire is as some fires burn at a hotter temperature than other fires.
Most lava is around 1,600 F degrees and some fires are hotter than that especially when it has a good fuel source.
Some fires can reach a temperature of 3,000 to 5,000 F degrees while other fires may only be 500 F or so degrees.
For example a fire in a wood burning stove would be around 500 to 700 F degrees at most while the Lava would be 1,600 F degrees which would be too hot for a wood stove fire.
A campfire would be around 250 F to 500 F degrees depending on how big the fire is.
The bigger the fire the hotter the fire and the smaller the fire the less hot the fire is.
So in that case Lava is usually hotter than fire.