The slide will not be nearly as tight as, say, an accurized 1911, but "loose" is a pretty broad term. The weakness of the older 226's is their frame rails. Take the slide off of the frame and visually inspect the frame rails closely...with a magnifying glass if possible. Any cracks will almost always start in the upper corners of the rails, and usually forward of the mag well...toward the front end of the frame. They are best seen from the inside of the frame. I have only seen four with rails cracked, so I am certainly no expert. Two of those were Secret Service guns that they said they were going to shoot to destruction...the slides flopped all around and they were inaccurate, but they never malfunctioned. The other two were personal weapons of officers who sent then back to Sig and were given brand new guns in return.
This was pretty much stopped cold when Sig beefed up the frame rails later...can't recall the serial number at which they changed, but it is on the back of later Safariland #070 holsters since the older holsters would not work well with the new frame series...too thick. Chances are that your gun is fine. Very, very few 226's show up with cracked rails...even the very oldest ones...and if yours' are, by chance, actually cracked, I am sure Sig will make it right.