Have you got a PC/Xbox currently? They're are some really great multi-platform games that are also worth considering as well in addition to the PS5 titles.
For me, the PS5 titles that are 'must plays' are:
- Astros Playroom (genuinely can't express how fun this game is and a great intro to the controller)
- Horizon Forbidden West (provided you've played Zero Dawn)
- Ratchet & Clank: Rift Apart (I don't think it matters if you've not played any previous Ratchet games)
- Spiderman & Miles Morales (more so worth playing as Spiderman 2 is out shortly. MM is a short game at 6 hours - Spiderman is a little longer!)
- The Last of Us Part 1 (may have already played the PS3 and PS4 version - but if not, it's unbelievable. I played it on PS3, skipped the PS4 remaster and picked this up and it's such a great story driven game).
- Ghost of Tsushima (came out on PS4 but plays so much better on PS5).
- God of War Ragnarok (provided you've played God of War 2017. I'm not the biggest GoW fan, enjoyed both games but personally for me I prefer the others in this list - all opinion though, a friend of mine adores GoW and Ragnarok is probably his favourite game)
And cross-platform:
- Dead Space (took me back to being 19 again and playing this game with my flatmates at uni, great remake)
- Elden Ring (took me about 5 hours to get it and then I quickly sank 60 hours in...)
- Star Wars: Jedi Survivor (if you can get through some of the performance quirks, it's a great story and builds on the first game so much)
There are loads of others, I'm sure people will recommend Returnal, Demon's Souls, FF7, Gran Turismo etc. but the above are the games that I've enjoyed the most on my PS5.