Pardon the long-winded story below. Suffice it to say I'm not sure I have a favorite. Read my backstory if interested.
My first bike was a '72 Honda 500-4. I was a young rider in the neolithic age of communication (pre web, let alone pre social media) and didn't know what I should have to really take advantage of that engine's power band. It wasn't that it made huge power by any means, but it had this very cool slippery feel at about 6 grand that I didn't really explore much.
I owned a few more I-4s but they didn't impress. Then I had a VFR 500 and that engine had a great sound, good vibes and was surprisingly fast (recorded my highest top speed on it). But then I had a '91 VFR with a Yoshi muffler - what a great sound! The bike was heavy and hot, on the downside.
The V-twin in my Super Hawk was pretty nice. I liked its relative simplicity and narrow build. The power was sufficient and it felt a bit more present than the V-four, a lot more than my I-4s. I owned it the longest. But then I had a DL1000 that I got cheap. The prior owner, a shop employee, didn't know how to sync the carbs and thought the bike was bad. I synced the carbs, but I never got on well with the engine's vibes and noisy clutch.
I'm currently on a Triumph triple and I really like the engine. I like its power and its vibes. I also like the simplicity of it compared to 2 & 4 V layouts (one valve cover, one timing chain, two camshafts). It may be my favorite bike of 'em all, and yet I kind of feel like I should try some other configurations before I'm done, like a good parallel twin (I had a bad one once), an L-twin, or a transverse V. I've never owned a boxer either, so ...