The E30 is the prettiest & they seem to last forever BUT it not ideal for daily driving & that M20 motor has a sound that not many cars can match. it a must have for every BMW lover though.
The E46 is the worst for me. It feels as though the build quality is not up to scratch. The interior bits always get scratches (centre console to ashtray section) & roof sags & the A pillar material comes loose.
BUT it has the best legroom in the rear & the boot is more than ample
The E36 imo is the best allrounder. Motors are fairly strong, build quality is good enough & if you have the M3 version, it should be fast enough as well.
My M3 has the same km as my E46 318i but the E36 just feel fresher inside.