This depends a LOT on whether you mean
a) "can sing along to songs with ease as you're listening to them"
or
b) "can remember most of the lyrics most of the time, if you get some a bit of the the melody and maybe the first words"
c) "could remember all the lyrics to even when woken up in the middle of the night at gunpoint and told to sing or die"
a) Thousands? No idea, tons and lots, mostly songs I couldn't care less about. Probably similar to some people who are in bands I'm guessing, just comes easily. I also listen a lot to music where the lyrics are relevant. Just looking at the CD's I own, this is easily in the many hundreds.
b) Hundreds. Mostly in Finnish. Lots of stuff like Christmas songs, naughty folk songs, drinking songs...
c) I thought there would be many more, but when I tried doing some, I noticed that generally I can't figure out how they start without the musical cues, or maybe I'm missing a verse or something. At least right now when I'm slightly tired this was a problem.
Here's what I came up right now in English.
- Bohemian Rhapsody by Queen (obviously)
- Hello I Love You by Doors
- People Are Strange by Doors
For my fellow Finns, I could of course mention artists like
YUP,
Ismo Alanko,
CMX and other such pillars of musical credibility. However, I think it would be more amusing that:
- I can easily do most
Raptori songs from the first two albums, and when very drunk we occasionally sing these with a couple of my friends
- I can all the "best"
Matti Nykänen songs