No. The fact is, unless we're talking about a wandering, dilapidated ship like the one in district 9, they don't need anything we have. If they found us, that means they have space travel far beyond ours. Our space travel is practically a box car compared to theirs, and as such, it's highly unlikely we have anything they haven't already got/done better. It'd most likely, be more trouble than it's worth to invade.
The only other possibilities for conflict are if we shot first (which would be stupid. I'm pretty cynical, but I'd think, and hope, we're not that dumb) or if the aliens took offense to us for some religious or idealogical reason.
Of course, if we found the aliens first, then perhaps human greed would take over. I doubt it though. Once we have far reaching space travel, why the hell do we have to go for the inhabited planet's resources?