It would help to know what kind of travel you normally do or what travel you plan on doing.

Rimowa is of course great, albeit very expensive. It would be a very high end gift, especially a full set. Topas sets, for instance, will run into the thousands of dollars price range. I am not as big of a fan of the Rimowas due to denting and the fact that they start to look very used after only a few trips of commercial aircraft travel. They are so expensive and get beat to hell. I also think that the Rimowas are a pain to get fixed under warranty or for dent removal, depending on where you live.

Tumi is another excellent option. It is understated (unlike the Rimowa, IMO) and appropriate for a wide range of personal and business travel. Great warranty, lots of boutiques where you can get luggage dropped off/ worked on for repair. Less expensive and generally very durable. The Alpha line is always a solid choice.

If you're more adventurous or do a lot of outdoorsy travel, I would strongly suggest the North Face Base Camp line of rolling suitcases (called Rolling Thunder) or the rolling Patagonia Black Hole bags. Both are pretty much entirely waterproof and incredibly durable. Great (lifetime) warranties. Really can't go wrong but won't have the same luxurious reputation as Rimowa or Tumi.

Hope this helps and congratulations!