Focus on CryptoNote-based coins: Monero, Electroneum, Sumokoin are some of them. These are still profitable with modern CPUs. Hashrate of a given CPU will be the same over any CryptoNote-based cryptocurrency.
[0] https://whattomine.com/ [1] http://monerobenchmarks.info/
Edit: Just to add some real numbers. My home desktop is based on a Ryzen 1700. It is currently overclocked @ 3.4 GHz. I can get mine around $1.60/day worth of Electroneum at current prices. Estimated TDP is <80W (CPU alone), which at SoCal electricity costs results in $0.30/day. Profit is then around $1.30 a day.
The first hit was for https://arxiv.org/pdf/1605.01354.pdf .
> We assumed that miners in the market at initial time ... own a personal PC such as Core i5 2600K, and hence they are initially endowed with a hashing capability ... equal to 0.0173GH/sec, that implies a power consumption equal to 75W
as well as:
> Over time, the different mining hardware available was characterized by an increasing hash rate, a decreasing power consumption per hash, and increasing costs. For example, NVIDIA Quadro NVS 3100M, 16 cores, belonging to the GPU generation, has a hash rate equal to 3.6 MH/s and a power consumption equal to 14 W [16]; ModMiner Quad, belonging to the FPGA generation, has a hash rate equal to 800 MH/s and power consumption equal to 40 W [16]; Monarch(300), belonging to the ASIC generation, has a hash rate equal to 300 GH/s and power consumption equal to 175 W
Using those numbers to give hash/Joule (a watt is a Joule/second):
CPU = 17.3MH / 75 W = 0.23 MH/J
GPU = 3.6 MH/s / 14 W = 0.25 MH/J
FPGA = 800 MH/s / 40 W = 20 MH/J
ASIC = 300000 GH/s / 175 W = 1700 MH/J
There's a bajillion other cryptocurrencies these days. The economics is different for every one.
Why don't you run a miner on your computer and find out.
If you're paying for your energy and equipment it'll most likely be a negative in terms of profit but would be a fun experiment and espouse a hacker ethos.
Plenty of perfectly fine working rackmount servers are replaced every year because for their power/space footprint you can put something that's about to do 50% more work.
Otherwise an accountant would tell you it is something like the cost of ownership: Let say very roughly $0.5 per cpu/per day.