Much of downtown Bonn is a pedestrian zone and walkable from the Bonn Hbf, which is also a major U-Bahn station. If you leave the station facing the center of town and go to the right, there's a hotel on the corner of Kaiserplatz. There's another one on almost the same street but on the other side of the tracks, IIRC at the corner of Bonnertalweg and Poppelsdorfer Allee. They're both modern business hotels, four star, convenient, and should have good internet. I think they're sister properties or otherwise related.

If you leave the station facing town and walk toward the left, there's an interesting looking hotel that seems to be built into an old brick school or monastery. Another interesting historic hotel idea would be Hotel Stern, located on Marketplatz just next to the old city hall building.

There are also modern business hotels just across from the train station, located almost at the main bus station, and on the back side of the station, but IMO they don't seem very attractive.

Any of these would be close to lots of restaurants, etc. I'm sorry I don't remember names.

There's an elegant looking small hotel on the first ring road north north east of downtown, but I don't think its location is so convenient for walking, trains, or subway.

However, the properties along the river aren't so convenient IMO, even though the views can be pleasant.

Bad Godesberg has a hotel built into the old castle walls. It's a pleasant place with restaurants, etc. but again I don't find it as convenient as being near the main train station.