In Dhrystone, which is pure Integer, they do. But add in floating point calculations (Whetstone) and ARM is beaten by leaps and bounds. Considering videogames are very reliant on floating point (Whetstone), the X86 still easily trumps ARM in gaming operations.
Coremark is almost totally Dhrystone, hence why ARM seems to keep up well with X86 in those benchmarks. But anything with heavy floating point usage will kick down ARM scores compared to X86.
Also depends on the precision of the integers and floats.
With that in mind... We need to remember that Apple's ARM chips are still pretty potent all things considered, especially when we take into account the TDP these chips run at.
Unrestrict that... And have it on a process with transistors optimized for frequency and then it's an entirely different ball game.
Still. I wouldn't under-estimate ARM's capability to scale upwards, we just haven't seen a company take the ISA and drive it into the super high-end yet.
It doesn't matter much between FP16,32 or 64, as ARM is built with Integer in mind, hence why all the official benchmarks were Dhrystone. FP was thought to be the (almost exclusive) domain of coprocessors until the Cortex line and still isn't used more prominently, as it needs much more complex chips and instructions (which in turn would also strongly increase consumption).
I agree, on a per-Watt-basis, ARM should trump X86. However, the architecture runs into a TDP wall around 2.5 Ghz, meaning that at 3 Ghz or more an X86 chip would probably be less consuming than an ARM processor. To get past those 3Ghz they would need to lengthen the pipeline, which risks costing some IPC if they would need to lengthen too much (essentially what happened with the Pentium 4).
I wouldn't say it's impossible to make some high-end ARM chip, but it would need some hefty changes; changes which would kill it's edge in the smartphone and tablet markets.
While on those tests ARM had to emulate X86, costing some performance, it still can only compete with the Atom N3450, which is also clocked slower than the Snapdragon 835 (Atom: 1.1 Ghz base 2.2 Ghz turbo; Snapdragon 1.9Ghz LITTLE 2.45Ghz big - and potentially can work together for 8 threads total against only 4 in the Atom) and get's trounced by a Core m3 6Y30 (900 Mhz base, 2.2 Ghz max. Singlecore turbo, 3.8W TDP), even in the native, non-emulated tests.
In other words, ARM still has a long way to go until it can keep up with x86 in power. But let's see how the new Cortex A75 and especially A76 Cores will perform, the Cryo 280 in the Snapdragon 835 are still based on the by now slightly outdated Cortex A73