You should play 5E. It's the best edition since the greatness of 4th.
We don't actually play pure 3.5, but rather a homebrewed 3.5/Pathfinder blend campaign setting with some minor other stuff mixed in (tibdbits from Call of Cthulhu, D20 Modern), which has grown over the last 15 years or so, and which I share with another DM (we rotate the duty).
I'm pretty sure I won't convince him to switch systems entirely. We have a vast amount of background material, characters and other stuff that would be a daunting task to update mechanically, which neither of us have the time to do. Also, I'm rather fond of the insane splatbook and supplemental materials support 3.5/Pathfinder has. Going to take a look at stuff we could backport tho. We've been doing it for years, so it wouldn't be a hard sell.
How are clerics faring in this new world of 5th edition? can I be a proper evil necromancer cleric leading my undead legion? Possible progression into Lich?
are evil PCS in general back in support again? because that disappointed me looking at 4th edition
The Death Domain for Clerics, Oathbreaker for Paladins, Assassin for rogues, Fiend Pact for Warlocks and Necromancy School for Wizards are all perfectly valid edgelord choices.
There aren't really hard-coded alignment restrictions (With the exception of the Oathbreaker). Paladins don't even have alignment requirements anymore, instead they have oaths whose tenets they must abide. You can skirt them a little, but if you break them often or blatantly you fall. Even then, falling is usually temporary if you work to redeem yourself.