For people who have seen the Rolling Stones often before, it must be terribly tempting to regard them today as geriatric hacks. Compared with the thrilling impact they exerted on popular consciousness a decade ago, when Mick Jagger and Keith Richards were widely and seriously believed to have some sort of tangible sympathy with the Devil, their shows today can seem like pandering to a teenage audience a generation younger than they.

This writer felt a bit of those feelings at the outset of the band's first of five New York area performances on Thursday night at the Brendan Byrne Arena in the New Jersey Meadowlands. The Stones came on and launched immediately into ''Under My Thumb,'' and there was Mr. Jagger cavorting determinedly and shouting the words unintelligibly, while the band set up a muddy racket of sound. It looked to be a long night.

It wasn't. Within a few minutes, things improved notably, and by the end this had become a not just enjoyable but positively refreshing experience. A long way from the Devil, maybe, but a decent step in the other direction.

The first thing that improved was the sound. The Byrne Arena is reputed to be the best local arena for music, but at the outset, at least from this writer's seat, the sound was poor. It cleared up enough by a half-hour into the set, however. In addition, this was the least deafeningly amplified arena show this writer has ever heard -which is meant as a compliment, not a complaint.

A few specifics: Tina Turner was the opening act, and joined the Stones for ''Honky Tonk Women.'' The Stones' set lasted slightly more than two hours. It consisted of 45 minutes of fast songs, 30 minutes of ''slow'' songs -''slow'' because Stones ballads tend to be as tough as their uptempo efforts -and another 45 minutes of fast numbers. The band played more of their real oldies, as well as familiar songs from the 1970's, than ever before. Aside from the band's basic five, there were two keyboard players (including the ''sixth Stone,'' Ian Stewart) and a saxophone player. An expensive and complex camera array, as well as sometimes annoying lighting, meant a film was being shot. The set is clever but less complex than some past Stones sets (the unfolding flower-petal from 1975, for instance). It was also adorned with a curiously tacky chiffon confection; the Stones' graphic elegance seems to be partly a thing of the past, although the tour poster remains handsome. The only encore (''Satisfaction'') was followed by an indoor fireworks display to Jimi Hendrix's version of ''The Star-Spangled Banner'' that effectively precluded a demand for more music.

All of this avoids the issues of how the band actually looked and sounded and what the whole evening meant. The answer to the first question is: fine. Mr. Jagger is in superb physical shape this year and, for all his mugging and restless peregrinations, is for the most part actually singing more carefully than he sometimes has. And the band is just as loose but tight as ever.

The answer to the second question will vary for every observer. This writer never got caught up entirely in the grander, late-60's vision of the Stones as instruments of darkness. Art was enough: they were and are a wonderful band, white men playing black music in a faithful but original way, and today they mix professionalism with inspiration in a manner that younger groups might well emulate. By and large, even with the hoariest oldies, the Stones' new versions extend one's memories, rather than denying them.

At the end, before the fireworks, bags of balloons on the ceiling are released, and first the air, then the audience and the stage, are crowded with balloons of every color. The metaphor is circusy and childlike. It purges lingering cynicism and, improbably enough, for all its evident calculation Mr. Jagger's showmanship, takes on an aura of innocent play.

Illustrations: photo of Mick Jagger