So lets start at the beginning. What type of music are you playing? If it's heavy metal, grunge, hard rock or rap you will never get it to sound good. In order for it to sound good you need to be playing old country, 60's rock n roll of blues (ha ha)
As it was mention, above, be sure that your guitar is in tune to what you are listening too. Standard tuning is E, A, D, G, B & E. (low to high). Some songs could be in a open tuning and will sound different. Make sure that you are playng to the same rythem / tempo as what you are listening, too. Some songs are played in a higher octave key than listed - if a song is called out in the Key of A it can be played with the open chords of A, D & E. Or it could be played with a capo on the 2nd fret and played with the chords of G, C & D. Same key being played at different location to match the singers voice.
Learn the song with the chord changes in the right locations - then make it yours by changing the Key to match your voice of whomever will be singing the song. Any song can be transposed.