Why is SHA3 less conducive to ASIC? Bitcoins are encrypted with SHA-256, and Ethereum is encrypted with SHA3.  Why can miners for SHA-256 encryption guess hashes in the TH/s when miners for the SHA3 encryption can only hash in the MH/s?  Is the algorithm more complex?
I'm not an expert but I'm a good at digging through academic literature, and this is what I found about SHA3 with relevance to FPGAs and ASICS (and in comparison with SHA2).



Note that this paper dates back from 2011, the winner of SHA3 was not yet decided as NIST only released the SHA3 standard in 2015. Take a look at the Keccak result in this paper. The ASIC space, atleast ASICs with the specific purpose of hashing, have evolved a lot the past 6 years and the numbers are probably not up to date.


  These  graphs (and  the  corresponding  tables) have revealed that Keccak is the only candidate that consistently outperforms SHA-2 for all considered FPGA families and two hash function variants (with 256-bit and 512-bit output). 




Another paper, which is also pretty old and dates back to 2010 has indications that Keccak (SHA3) is faster than SHA-256.


  Figure 5 illustrates how architecture differences affect the performance results. Some curves, like those of Keccak and Luffa, are very steep. This means that a small increase in area yields a significant performance improvement.




Also, I'm not aware of any ASICs for Ethereum, they are currently being mined using GPU's. As you probably already know: GPU's are magnitudes slower than ASICs thus being in MH/s range is no surprise.