Well, as you increase your terminal's rows/columns, each character starts to approximate a pixel. The included screenshot is around 50 rows (double the "normal" ~80x24). Emoji and Unicode can probably stretch this further.
I'd love to see more quality terminal apps come out. I feel like the software (excepting, of course, the browser) I use is perfectly bifurcated into "terminal" and "webapp" domains. I just don't see to have much use for traditional GUIs anymore and even prefer locally hosted webapps to them.
In htop 2 and higher [1], you can enable graph history mode by pressing the space bar twice to change meter style on the relevant meter in the setup (F2). It works for CPU, RAM, load, swap…
