i have some 80 - 90 legacy lenses
i would say the contax G90 2.8 ls very sharp but has to much contrast, so it is not so good for portrait but very good for landscape etc.
for portrait very good is the leica summicron 90mm
also very good is the Sony 85mm and has AF (with sony adapter) but contrast and sharpness from the contax is much better but the sony is better
for portrait but not as good as the summicron but o.k.
awesome is the mamiya 80mm 2.8 and i think there is also a 80mm 1.9 (but more weight), it is a mediumformat lens but very light and manual focusing is like a dream...so smooth and precise .....and very sharp! and cheap but you need two adapters mamaya 645 to cannon or nikon and adapter to sony e-mount
the contax G90 has not such nice focussing so if you want the lens for landscape go for the C/Y 85mm or the mamiya because of smooth manualfocus, the mamaiya is a better allrounder..... portrait and landscape is great
if you want to spare money for the batis you could try the minolta MD 135mm 3.5, it is very small cheap and comes very close to the Contax G90