If you're talking about Heart (Purple) Genryusai, he's a nice starting character. Neutral attribute, boss killer, and a nice moveset for PVE as well as PVP. If it's the Power (Red) or Tech (Green) version, well...you could do better unfortunately.
If you're serious about re-rolling, I'd recommend waiting a few more days for the 2x gatcha at the end of the month. Dangai Ichigo, Hogyoku Aizen, and Barragan are coming then, and all three are amazing (and fan favorites). Not just that, you'll have a better chance to pull a 5*, since rates will be doubled at that time (for the three previously-mentioned characters, as well as a handful of other ones). Really, what you're after is one of the new characters and you'll be set.
Whatever you decide, is up to you. Just giving a bit of advice.
If it's the pull during the tutorial, you can only ever get a 3* from it. If it's the second pull you did, then yes, re-roll.
As mentioned above, waiting until the end of the month (another week) will give you access to three extremely strong characters. If you don't mind waiting until then to re-roll, that is.