You are:
Tennis
There's a match in my pocket / And an ace up my sleeve
Yet I'm no magician / That you can conceive
'match' and 'ace' are both common tennis terms
I'm admired in New York /London and more
Yet I am no God / And love is a chore
Major tennis tournaments occur in both cities. 'Love' is another tennis term, meaning 'no score,' which makes winning a game a bit of a chore.
You can set me on grass /Or mould me with clay
Yet all ties are broken/ At the end of the day
Tennis is played either on grass or clay. No tennis match ends in a tie. Furthermore, no game or set can end in a tie, all have rules for tiebreakers such as advantage, etc.