There is no perfect type of run up for a bowler. As a general rule, it should be pretty straight in the approach to the stumps but plenty of world class bowlers defy this convention. What is important is for a bowler to find the right rhythm during the run up.
For quicker bowlers, this will usually mean a gradual acceleration but there are plenty of examples of bowlers who have ambled in until a last explosive delivery stride. Or those who sprint in the full way. Whilst we urge caution if the run up is too quick or if there is not enough momentum gathered from it to help achieve the pace being sought, if it works, and it's not causing injury, why change it? Look at footage of any number of international bowlers past and present and you will see the run ups are various speeds, lengths and angles. All with the aim of getting the bowler into the right position to deliver the ball on arrival at the crease whilst still having decent forward momentum.
Spinners have even more variety in their run ups. Shane Warne walked up to the crease before a couple of hops into his delivery stride and hey presto, 708 Test wickets. Other spinners seem to glide in from six or seven paces before turning elegantly in their delivery stride onto their front leg and pivoting around it to deliver balls with turn and bounce. Whatever your bowling style, find the run up that best suits you, mark it out and use it every time.