Define... celebrate.
I go to costume parties because it's fun. They just happen around Halloween. If they were in any other month, I'd still go.
All Hallows Eve is a way to celebrate the dead for some, other people believe it is when the spiritual and physical realm are closest and wanna... talk to ghosts? ( I am unsure as I believe you should just leave dead people alone. Saul in the OT yelled at some dude for waking him up.) The holiday has Pagan origins brought over from Ireland, granted, our modern Christmas has pagan origins from South America... so.. y'know...
What bothers me is the fear factor. "For the Lord has not given us a spirit of fear" and part of Halloween feeds off of fear. Skeletons, morbid images of death, fake blood, monsters and stuff... not exactly Christ-like things.
The other bit is greed. Kids running around hassling people for candy, comparing how much candy they got, which house gives out the best candy, the most candy, how much candy can I consume without my parents noticing.
While there are worse activities out there, I don't think Halloween is optimal. I wouldn't call it WRONG, but I wouldn't call it right either. If you wanna hit up a costume party and gorge on individually wrapped Snickers bars go for it.
You wanna make some kid pee himself by popping out of a grave? Eh, then I question your interest in said holiday.