I'm guilty for having too many jerseys.
I have a ton of soccer jerseys, as you'd expect, most of which are Manchester United and Barcelona jerseys (but I'd say there are more United jerseys in the mix). I do have some soccer jerseys from different leagues though: (Glasgow) Celtic, England national team, LA Galaxy (both Beckham jerseys), Boca Juniors, Olympique Lyonnais, Marseille, Inter Milan (see I even have something from Italy). My ex-girlfriend is a die-hard Arsenal fan and I didn't mind the two Arsenal jerseys she bought me but I rarely wear them. I also have a retro West Ham shirt with Bobby Moore's #6 on it that a West Ham fan friend of mine has. My mom bought me a Real Madrid jersey 4 years ago and that didn't sit well with me, even if it was a prank and even it was David Beckham's jersey. I've been tempted to burn that shirt but it's in storage now where it'll never see the light of day.
With basketball, I only have Laker and North Carolina jerseys. With baseball, I have a retro Reggie Jackson California Angels jersey and two Dodgers jerseys and that's all. Wit football, I'm not a particular fan of any team, but I do like the Dallas Cowboys and I have three Cowboys jerseys, although I have a Baltimore Colts Johnny Unitas, San Diego Chargers Lance Alworth, a Los Angeles Rams Eric Dickerson, and a New York Jets Joe Namath. I don't have hockey jerseys (I used to have a Ducks, Red Wings, and Rangers though) while I don't wear caps much.
So, basically, I'll collect any jersey if it's not from a club in the same league and/or a hated rival, especially the latter.