Not on the Riverwalk, per se
Hotel Emma has recently opened in San Antonio's Pearl Brewery complex. It is technically on the Riverwalk in that you can walk next to the river to the main Riverwalk but is probably about a mile north of there. That said the Brewey area is more interesting than the tourist trap part. We only had a lovely lunch at the Emma but have not stayed there it looks nicer than the Westin (which I have stayed at).
When we lunched at the Emma, we were staying at the St. Anthony which was a pleasant experience--old hotel renovated recently. Also, a touch better than the Westin and not on the river but close access.
Have stayed at the Ritz NO twice in the dead of August and always enjoyed it--our travel agent always helped get us a nice upgrade (the place is really empty that time of year). We once stayed at the W French Quarter and it was the least dreadful W experience we've had and a step down from the Ritz but great location. The Windsor Court used to be the place to stay in the 90s, not sure how it has fared. I see LHW has one property (Le Pavillon) but never heard of it and don't love the location.