I've been playing guitar since I was 14. I own three guitars and play a couple of times a week - it's very therapeutic. But despite that, I'm not really that "good". I don't really know music so while over the years I have developed some ability play the guitar and my ear is pretty good so I can learn to play most songs I want to play (not including solos of course - I'm not a shredder, but riffs and chords progressions). But basically if I go more than a couple of weeks without playing it, it's gone forever and I would have to relearn the song.
If you can play chords and basic tabs, and just want to play (e.g. strum) and sing a song (mostly what I do), I like the (Edit - Ultimate Guitar) app. Set up and account an you get some good features and the ability to save favorites. They have formats ranging from basic chords over lyrics to full pro-tablature. Most songs have multiple postings in various formats but it displays which ones have the highest ratings - usually if you see five versions and the third one has five times as many approval ratings, it's the one to go with. It will also transpose or scroll (while playing) - which is cool, though those might be on the paid version only, not sure.