I've got 6 bikes now, so I guess you could call that a collection. My wife certainly would. I've also sold quite a few nice bikes over the years. My criteria, in approximate order of importance, are:
- Fit. If the bike isn't the right size and geometry for me, I don't give it a second-thought. Early on I had some bikes that didn't fit and I learned that lesson well.
- Function. I used to own mostly racing bikes (Merckx, Bianchi, Gios, De Bernardi) when most of my riding was fast group rides and occasional supported tours. Now my collection is mostly touring and sport touring bikes, with one cyclocross and one racing, because my riding is mostly commuting, touring and riding on greenways and trails.
- Finish. I try to buy frames that have paint and chrome that are in very good to excellent condition, because they are more appealing to me and I've found out how expensive it is have bikes repainted. The colors and decals also have to appeal to me. I don't buy ugly bikes, although I can understand their appeal for those who ride in high theft areas.
- Frame material. I like steel bikes, although I owned one ti bike (Merckx AX) that was very nice. If have no desire to own a carbon or aluminum bike. I had one AL bike and hated the way it rode, even with a carbon fork. I've ridden carbon bikes and didn't like the feel.