as you approach the high end cards, the performance/$ generally drops, so effectively less value. Depends what you mean by 'worth it'. If you have $500, then the 780 will perform better and will more likely max out all games at 1080, 60fps for longer. Whereas the 770 may not do with some current games or future ones. Have a look at reviews for the 770, to see if it maxes out all the games you want to play (assuming you want them maxed out).
Ik you've probably already bought the card, but the gtx 780 is a BIG WASTE of money, if you're playing on a 1080p monitor, all you need is a 770. If u play at 4k(which is un-necessary), then u need 780. Get a 770 and SLI it when it starts to get old. If you already have a 780, keep it for as long as you can before upgrading. Dont SLI it. There is a max diff of 8fps in crysis 3 on 770 SLI vs 780 SLI.
Considering your 1920x1080 monitor is probably 60Hz refresh, fps, you not notice any difference in majority of games. Only a select few ultra high intense games like BF4, or Bioshock, will the 780 have an edge. The higher fps output of the 780 will hold the @60 fps range better on max ultra settings.