To the best of my recollection, I'm one of the few people on here that has defended Wrestlemania XV as being at least, a decent Wrestlemania. Wrestlemania XV was basically a bigger hyped, extended Monday Night Raw of that era, which at the time I loved. It really depends on whether you were a fan of that period of wrestling. If you really enjoyed the exciting, but chaotic, sloppy booking style that was the Attitude Era, then you'll probably enjoy Wrestlemania XV for what it was. It's probably not a show that holds up very well, but it was a certainly a show of it's time, and at the time I enjoyed it immensely. While I think it's in the bottom 10 of all the Wrestlemanias, I certainly don't consider it the worst (Wrestlemania XI is still the worst ever). Wrestlemania XV wasn't about the matches on the card, it was about the overall show, and while it was chaotic, and even sloppy, and certainly lacking in great matches, it was an entertaining show at least.
With that said, Wrestlemania XIV is BY FAR a superior event, and IMO still to this day, one of the greatest ppv events in the history of WWE. There have been other ppv events that were more consistent with matches, but few events were able to combine, good, logical booking, with classic matches, and influence and impact on the history of the company. Wrestlemania XIV was the official kick-off of the Attitude Era. In a thread a few months ago, discussing the greatest ppv events in WWE history, I mentioned about Wrestlemania XIV, that while watching it, you truly felt you were watching the dawning of a new era in the company. With most ppv events that are important on the company's history, you go back years later and say "yeah, it was a pretty important show," but few you could genuinely say that as you were watching it. Wrestlemania XIV was one of those ppv events. Taker/Kane (IMO the best "big man/giant" wrestler match of all-time) and HBK/Stone Cold are amongst the best matches in Wrestlemania history, and the rest of the card was solid too with HHH/Owen Hart, Rock/Shamrock, the 15 team battle royal (I enjoy all battle royals, no matter how insignificant they may be), and a great gem of a light heavyweight match between Taka Michinoku and Aguila. Wrestlemania XIV, isn't just vastly superior to Wrestlemania XV, it's one of the best Wrestlemanias ever (top 5 for sure), and one of the best events in the company's history (top 10 probably).
So in short, though Wrestlemania XV isn't amongst the worst ppv events in history, it's certainly nowhere near the level of Wrestlemania XIV.