The answer (or lack of an answer) depends on your definition of god. I can't believe that the aliens would pass as a creator deity in this cynical age. A pantheon of specialist gods sounds equally unlikely.
What they could try is to pass themselves as mortal beings with "refined spiritual qualities" that border on a godlike status. Gurus, not gods.
- Start by demonstrating feats beyond science as we know it. Heal the lame, turn water into wine, raise the death. They should insist that this is a mental power, not technology, and that everybody can learn it. Or at least a select few. Of course there would be hidden technological gadgets behind these miraces.
- Then teach a few selected followers. Make sure that there is a lot of deep mediation and one-on-one training is involved. Give those followers lesser powers, but never the full suite.
- React in sorrow to this limited progress. Mankind isn't wise enough. They aliens are better, even if they would never be so crass to say it. Just look at their obvious pain as their human pupils fail to walk on water, again. While their teachers make it seem easy.