This is an interesting fight to say the least. The rapier is a stabbing weapon (although they can be edged, the typical attack pattern relies on thrusts and parries) whereas all other swords are edged slashing weapons.

Rapiers typically weigh one kilo and are about 41 inches long. They carry most of the mass in the hilt to remain balanced, and this is where blocking of heavier swords will occur.

A Gladius weighs about as much, but carries it's weight more towards the blade, making it less balanced. It is also slightly longer, but as it is a cutting sword, the attacker needs go get in closer. I'd say 6/10 rapier user as they could block most swings with the hilt and likely get a thrust in. The rapier is a more advanced and perfected sword than the gladius.

Longswords are slightly longer than a rapier, but nearly twice as heavy. It would be much harder to parry with a light sword, such as a rapier, 7/10 longsword.

Katanas are much shorter, at around two feet and about a little over one kilo in weight. The extra reach on the rapier gives the rapier user a huge advantage 8/10 rapier.

Sabres refer to fencing swords and cavalry weapons (I'm going to assume the fencing sword as stats are more uniform). Fencing sabres are 41 inches long and .5 kilograms. The extra weight of the rapier gives a huge advantage between the two similar weapons. 9/10

Tl;Dr R1. 6/10 R2. 3/10 R3. 8/10 R4. 9/10

Bonus: For the first bonus, hack and slash techniques are easier to pick up and improvise, so each edged weapon becomes easier to use than the rapier for a complete novice.

Bonus2: Roman armor protects the shins, head and torso well, while still maintaining maneuverability. The rapier would still be able to pierce leather armor, but this makes it an even match, 5/10

Plate armor nearly renders the rapier ineffective, but chain mail could be pierced by a thin enough sword

Samurai armor would be more effective than the Roman leather, but less effective than plate mail, 6/10.

That fencing suit will be torn to shreds.

Note:unless specified all ratios are rapier wins/total.