No of course not.. The only thing you might run into is the fact that most adults 25+ have familes and generally busy lives, so it migth be hard to put in the hours at work some companies demand from their "just out of art school and living living on Top Raman while working 16 hour days" younger recruits.
I was just watching a Richard Schmid painting video and during the Q and A he mentioned that back in the day, artists were widely regarded as not fully coming into their own until 50 or 60 - although he mentioned that a few guys like John Singer Sargent did some good work in his later 20's and early 30's. That sorta cracks me up because so often the fields of games and film are a huge draw to younger people and associated with youth, yet it's clear from looking at the great masters that one's artistic faculties and skills can progress way into senior age.
Anyway.. as long as you have the time to commit to it, there is no reason you can't make great progress and achieve your goals. Oh yea.. portfolio is the key factor in getting work (aside from your personality and connections and friends etc.). Going to a great school MIGHT help, but by far your body of work speaks most loudly. Secondly would be having worked on high profile projects or at recognized companies which proves you have the qualities needed to get a job done. That's hard to do when one first starts out, but the same rule applies to everyone regardless of age.